An experiment is a procedure carried out to support, refute, or validate a hypothesis. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated. Experiments vary in goal and scale, but always rely on repeatable procedure and logical analysis of the results. There exists natural experimental studies. A child may carry out basic experiments to understand gravity, while teams of scientists may take years of systematic investigation to advance their understanding of a phenomenon. Experiments and other types of hands-on activities are important to student learning in the science classroom. Experiments can raise test scores and help a student become more engaged and interested in the material they are learning when used over time. Experiments can vary from personal and informal natural comparisons, to controlled. Uses of experiments vary between the natural and human sciences. Experiments include controls, which are designed to minimize the effects of variables other than the single independent variable.
This increases the reliability of the results through a comparison between control measurements and the other measurements. Scientific controls are a part of the scientific method. Ideally, all variables in an experiment are controlled and none are uncontrolled. In such an experiment, if all controls work as expected, it is possible to conclude that the experiment works as intended, that results are due to the effect of the tested variable. In the scientific method, an experiment is an empirical procedure that arbitrates competing models or hypotheses. Researchers use experimentation to test existing theories or new hypotheses to support or disprove them. An experiment tests a hypothesis, an expectation about how a particular process or phenomenon works. However, an experiment may aim to answer a "what-if" question, without a specific expectation about what the experiment reveals, or to confirm prior results. If an experiment is conducted, the results either support or disprove the hypothesis.
According to some philosophies of science, an experiment can never "prove" a hypothesis, it can only add support. On the other hand, an experiment that provides a counterexample can disprove a theory or hypothesis, but a theory can always be salvaged by appropriate ad hoc modifications at the expense of simplicity. An experiment must control the possible confounding factors—any factors that would mar the accuracy or repeatability of the experiment or the ability to interpret the results. Confounding is eliminated through scientific controls and/or, in randomized experiments, through random assignment. In engineering and the physical sciences, experiments are a primary component of the scientific method, they are used to test theories and hypotheses about how physical processes work under particular conditions. Experiments in these fields focus on replication of identical procedures in hopes of producing identical results in each replication. Random assignment is uncommon. In medicine and the social sciences, the prevalence of experimental research varies across disciplines.
When used, experiments follow the form of the clinical trial, where experimental units are randomly assigned to a treatment or control condition where one or more outcomes are assessed. In contrast to norms in the physical sciences, the focus is on the average treatment effect or another test statistic produced by the experiment. A single study does not involve replications of the experiment, but separate studies may be aggregated through systematic review and meta-analysis. There are various differences in experimental practice in each of the branches of science. For example, agricultural research uses randomized experiments, while experimental economics involves experimental tests of theorized human behaviors without relying on random assignment of individuals to treatment and control conditions. One of the first methodical approaches to experiments in the modern sense is visible in the works of the Arab mathematician and scholar Ibn al-Haytham, he conducted his experiments in the field of optics - going back to optical and mathematical problems in the works of Ptolemy - by controlling his experiments due to factors such as self-criticality, reliance on visible results of the experiments as well as a criticality in terms of earlier results.
He counts as one of the first scholars using an inductive-experimental method for achieving results. In his book "Optics" he describes the fundamentally new approach to knowledge and research in an experimental sense: "We should, that is, recommence the inquiry into its principles and premisses, beginning our investigation with an inspection of the things that exist and a survey of the conditions of visible objects. We should distinguish the properties of particulars, gather by induction what pertains to the eye when vision takes place and what is found in the manner of sensation to be uniform, unchanging and not subject to doubt. After which we should ascend in our inquiry and reasonings and orderly, criticizing premisses and exercising caution in regard to conclusions – our aim in all that we make subject to inspect
Isotopes are variants of a particular chemical element which differ in neutron number, in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom; the term isotope is formed from the Greek roots isos and topos, meaning "the same place". It was coined by a Scottish doctor and writer Margaret Todd in 1913 in a suggestion to chemist Frederick Soddy; the number of protons within the atom's nucleus is called atomic number and is equal to the number of electrons in the neutral atom. Each atomic number identifies a specific element, but not the isotope; the number of nucleons in the nucleus is the atom's mass number, each isotope of a given element has a different mass number. For example, carbon-12, carbon-13, carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, 14, respectively; the atomic number of carbon is 6, which means that every carbon atom has 6 protons, so that the neutron numbers of these isotopes are 6, 7, 8 respectively.
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example carbon-13 with 6 protons and 7 neutrons. The nuclide concept emphasizes nuclear properties over chemical properties, whereas the isotope concept emphasizes chemical over nuclear; the neutron number has large effects on nuclear properties, but its effect on chemical properties is negligible for most elements. In the case of the lightest elements where the ratio of neutron number to atomic number varies the most between isotopes it has only a small effect, although it does matter in some circumstances; the term isotopes is intended to imply comparison, for example: the nuclides 126C, 136C, 146C are isotopes, but 4018Ar, 4019K, 4020Ca are isobars. However, because isotope is the older term, it is better known than nuclide, is still sometimes used in contexts where nuclide might be more appropriate, such as nuclear technology and nuclear medicine. An isotope and/or nuclide is specified by the name of the particular element followed by a hyphen and the mass number.
When a chemical symbol is used, e.g. "C" for carbon, standard notation is to indicate the mass number with a superscript at the upper left of the chemical symbol and to indicate the atomic number with a subscript at the lower left. Because the atomic number is given by the element symbol, it is common to state only the mass number in the superscript and leave out the atomic number subscript; the letter m is sometimes appended after the mass number to indicate a nuclear isomer, a metastable or energetically-excited nuclear state, for example 180m73Ta. The common pronunciation of the AZE notation is different from how it is written: 42He is pronounced as helium-four instead of four-two-helium, 23592U as uranium two-thirty-five or uranium-two-three-five instead of 235-92-uranium; some isotopes/nuclides are radioactive, are therefore referred to as radioisotopes or radionuclides, whereas others have never been observed to decay radioactively and are referred to as stable isotopes or stable nuclides.
For example, 14C is a radioactive form of carbon, whereas 12C and 13C are stable isotopes. There are about 339 occurring nuclides on Earth, of which 286 are primordial nuclides, meaning that they have existed since the Solar System's formation. Primordial nuclides include 32 nuclides with long half-lives and 253 that are formally considered as "stable nuclides", because they have not been observed to decay. In most cases, for obvious reasons, if an element has stable isotopes, those isotopes predominate in the elemental abundance found on Earth and in the Solar System. However, in the cases of three elements the most abundant isotope found in nature is one long-lived radioisotope of the element, despite these elements having one or more stable isotopes. Theory predicts that many "stable" isotopes/nuclides are radioactive, with long half-lives; some stable nuclides are in theory energetically susceptible to other known forms of decay, such as alpha decay or double beta decay, but no decay products have yet been observed, so these isotopes are said to be "observationally stable".
The predicted half-lives for these nuclides greatly exceed the estimated age of the universe, in fact there are 27 known radionuclides with half-lives longer than the age of the universe. Adding in the radioactive nuclides that have been created artificially, there are 3,339 known nuclides; these include 905 nuclides that are either stable or have half-lives
A bacteriophage known informally as a phage, is a virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν, "to devour". Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome, may have simple or elaborate structures, their genomes may encode as many as hundreds of genes. Phages replicate within the bacterium following the injection of their genome into its cytoplasm. Bacteriophages are among the most diverse entities in the biosphere. Bacteriophages are ubiquitous viruses, found, it is estimated there are more than 1031 bacteriophages on the planet, more than every other organism on Earth, including bacteria, combined. One of the densest natural sources for phages and other viruses is seawater, where up to 9x108 virions per millilitre have been found in microbial mats at the surface, up to 70% of marine bacteria may be infected by phages, they have been used for over 90 years as an alternative to antibiotics in the former Soviet Union and Central Europe as well as in France.
They are seen as a possible therapy against multi-drug-resistant strains of many bacteria. Phages of Inoviridae have been shown to complicate biofilms involved in pneumonia and cystic fibrosis and shelter the bacteria from drugs meant to eradicate disease, thus promoting persistent infection. Additionally, Inoviridae leave the host cell intact meaning that they can not be used medically anyway. Bacteriophages occur abundantly in the biosphere, with different genomes, lifestyles. Phages are classified by the International Committee on Taxonomy of Viruses according to morphology and nucleic acid. Nineteen families are recognized by the ICTV that infect bacteria and archaea. Of these, only two families have RNA genomes, only five families are surrounded by an envelope. Of the viral families with DNA genomes, only two have single-stranded genomes. Eight of the viral families with DNA genomes have circular genomes. Nine families infect bacteria only, nine infect archaea only, one infects both bacteria and archaea.
It has been suggested that members of Picobirnaviridae infect bacteria, not mammals. In 1896, Ernest Hanbury Hankin reported that something in the waters of the Ganges and Yamuna rivers in India had marked antibacterial action against cholera and could pass through a fine porcelain filter. In 1915, British bacteriologist Frederick Twort, superintendent of the Brown Institution of London, discovered a small agent that infected and killed bacteria, he believed. Twort's work was interrupted by shortage of funding. Independently, French-Canadian microbiologist Félix d'Hérelle, working at the Pasteur Institute in Paris, announced on 3 September 1917, that he had discovered "an invisible, antagonistic microbe of the dysentery bacillus". For d’Hérelle, there was no question as to the nature of his discovery: "In a flash I had understood: what caused my clear spots was in fact an invisible microbe … a virus parasitic on bacteria." D'Hérelle called the virus a bacteria-eater. He recorded a dramatic account of a man suffering from dysentery, restored to good health by the bacteriophages.
It was D'Herelle who conducted much research into bacteriophages and introduced the concept of phage therapy. In 1969, Max Delbrück, Alfred Hershey and Salvador Luria were awarded the Nobel Prize in Physiology or Medicine for their discoveries of the replication of viruses and their genetic structure. Phages were discovered to be antibacterial agents and were used in the former Soviet Republic of Georgia during the 1920s and 1930s for treating bacterial infections, they had widespread use, including treatment of soldiers in the Red Army. However, they were abandoned for general use in the West for several reasons: Antibiotics were discovered and marketed widely, they were easier to store and to prescribe. Medical trials of phages were carried out, but a basic lack of understanding raised questions about the validity of these trials. Publication of research in the Soviet Union was in the Russian or Georgian languages and were not followed internationally for many years; the use of phages has continued since the end of the Cold War in Georgia and elsewhere in Central and Eastern Europe.
The first regulated, double-blind clinical trial was reported in the Journal of Wound Care in June 2009, which evaluated the safety and efficacy of a bacteriophage cocktail to treat infected venous ulcers of the leg in human patients. The FDA approved the study as a Phase I clinical trial; the study's results demonstrated the safety of therapeutic application of bacteriophages but did not show efficacy. The authors explain that the use of certain chemicals that are part of standard wound care may have interfered with bacteriophage viability. Another controlled clinical trial in Western Europe was reported shortly after this in the journal Clinical Otolaryngology in August 2009; the study concludes that bacteriophage preparations were safe and effective for treatment of chronic ear infections in humans. Additionally, there have been numerous animal and other experimental clinical trials evaluating the efficacy of bacteriophages for
A model organism is a non-human species, extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Model organisms are used to research human disease when human experimentation would be unfeasible or unethical; this strategy is made possible by the common descent of all living organisms, the conservation of metabolic and developmental pathways and genetic material over the course of evolution. Studying model organisms can be informative, but care must be taken when generalizing from one organism to another. In researching human disease, model organisms allow for better understanding the disease process without the added risk of harming an actual human; the species chosen will meet a determined taxonomic equivalency to humans, so as to react to disease or its treatment in a way that resembles human physiology as needed. Although biological activity in a model organism does not ensure an effect in humans, many drugs and cures for human diseases are developed in part with the guidance of animal models.
There are three main types of disease models: homologous and predictive. Homologous animals have the same causes and treatment options as would humans who have the same disease. Isomorphic animals share the same treatments. Predictive models are similar to a particular human disease in only a couple of aspects, but are useful in isolating and making predictions about mechanisms of a set of disease features; the use of animals in research dates back to ancient Greece, with Aristotle and Erasistratus among the first to perform experiments on living animals. Discoveries in the 18th and 19th centuries included Antoine Lavoisier's use of a guinea pig in a calorimeter to prove that respiration was a form of combustion, Louis Pasteur's demonstration of the germ theory of disease in the 1880s using anthrax in sheep. Research using animal models has been central to many of the achievements of modern medicine, it has contributed most of the basic knowledge in fields such as human physiology and biochemistry, has played significant roles in fields such as neuroscience and infectious disease.
For example, the results have included the near-eradication of polio and the development of organ transplantation, have benefited both humans and animals. From 1910 to 1927, Thomas Hunt Morgan's work with the fruit fly Drosophila melanogaster identified chromosomes as the vector of inheritance for genes. Drosophila became one of the first, for some time the most used, model organisms, Eric Kandel wrote that Morgan's discoveries "helped transform biology into an experimental science." D. melanogaster remains one of the most used eukaryotic model organisms. During the same time period, studies on mouse genetics in the laboratory of William Ernest Castle in collaboration with Abbie Lathrop led to generation of the DBA inbred mouse strain and the systematic generation of other inbred strains; the mouse has since been used extensively as a model organism and is associated with many important biological discoveries of the 20th and 21st centuries. In the late 19th century, Emil von Behring isolated the diphtheria toxin and demonstrated its effects in guinea pigs.
He went on to develop an antitoxin against diphtheria in animals and in humans, which resulted in the modern methods of immunization and ended diphtheria as a threatening disease. The diphtheria antitoxin is famously commemorated in the Iditarod race, modeled after the delivery of antitoxin in the 1925 serum run to Nome; the success of animal studies in producing the diphtheria antitoxin has been attributed as a cause for the decline of the early 20th-century opposition to animal research in the United States. Subsequent research in model organisms led to further medical advances, such as Frederick Banting's research in dogs, which determined that the isolates of pancreatic secretion could be used to treat dogs with diabetes; this led to the 1922 discovery of insulin and its use in treating diabetes, which had meant death. John Cade's research in guinea pigs discovered the anticonvulsant properties of lithium salts, which revolutionized the treatment of bipolar disorder, replacing the previous treatments of lobotomy or electroconvulsive therapy.
Modern general anaesthetics, such as halothane and related compounds, were developed through studies on model organisms, are necessary for modern, complex surgical operations. In the 1940s, Jonas Salk used rhesus monkey studies to isolate the most virulent forms of the polio virus, which led to his creation of a polio vaccine; the vaccine, made publicly available in 1955, reduced the incidence of polio 15-fold in the United States over the following five years. Albert Sabin improved the vaccine by passing the polio virus through animal hosts, including monkeys, it has been estimated that developing and producing the vaccines required the use of 100,000 rhesus monkeys, with 65 doses of vaccine produced from each monkey. Sabin wrote in 1992, "Without the use of animals and human beings, it would have been impossible to acquire the important knowledge needed to prevent much suffering and premature death not only among humans, but among animals."Other 20th-century medical advances and treatments that relied on research performed in animals include organ transplant techniques, the heart-lung machine and the whooping cough vaccine.
Treatments for animal diseases have been developed, including for rabies, anthrax
In biology, offspring are the young born of living organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a progeny in a more general way; this can refer to a set of simultaneous offspring, such as the chicks hatched from one clutch of eggs, or to all the offspring, as with the honeybee. Human offspring are referred to as children. Offspring can occur after artificial insemination. Offspring contains many parts and properties that are precise and accurate in what they consist of, what they define; as the offspring of a new species known as a child or f1 generation, consist of genes of the father and the mother, known as the parent generation. Each of these offspring contains numerous genes which have coding for specific properties. Males and females both contribute to the genotypes of their offspring, in which gametes fuse and form. An important aspect of the formation of the parent offspring is the chromosome, a structure of DNA which contains many genes.
To focus more on the offspring and how it results in the formation of the f1 generation, is an inheritance called sex-linkage, a gene, located on the sex chromosome and patterns of these inheritance differ in both male and female. The explanation that proves the theory of the offspring having genes from both parent generations, is proven through a process called crossing-over, which consists of taking genes from the male chromosomes and genes from the female chromosome, resulting in a process of meiosis occurring, leading to the splitting of the chromosomes evenly. Depending on which genes are dominantly expressed in the gene will result in the sex of the offspring; the female will always give an X chromosome, whereas the male, depending on the situation, will either give an X chromosome or a Y chromosome. If a male offspring is produced, the gene will consist of a Y chromosome. If two X chromosomes are expressed and produced, it produces a female offspring. Cloning is the production of an offspring.
Reproductive cloning begins with the removal of the nucleus from an egg, which holds the genetic material. In order to clone an organ, a stem cell is to be produced and utilized to clone that specific organ. A common misconception of cloning is. Cloning copies the DNA/genes of the parent and creates a genetic duplicate; the clone will not be a similar copy as he or she will grow up in different surroundings from the parent and may encounter different opportunities and experiences. Although positive, cloning faces some setbacks in terms of ethics and human health. Though cell division and DNA replication is a vital part of survival, there are many steps involved and mutations can occur with permanent change in an organism's and their offspring's DNA; some mutations can be good as they result in random evolution periods in which may be good for the species, but most mutations are bad as they can change the genotypes of offspring, which can result in changes that harm the species. Lineal descendant Kinship Patrilineality Parental investment Parent–offspring conflict Litter Infanticide Clutch
Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA by the enzyme RNA polymerase. Both DNA and RNA are nucleic acids. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: RNA polymerase, together with one or more general transcription factors, binds to promoter DNA. RNA polymerase creates a transcription bubble; this is done by breaking the hydrogen bonds between complementary DNA nucleotides. RNA polymerase adds RNA nucleotides. RNA sugar-phosphate backbone forms with assistance from RNA polymerase to form an RNA strand. Hydrogen bonds of the RNA–DNA helix break, freeing the newly synthesized RNA strand. If the cell has a nucleus, the RNA may be further processed; this may include polyadenylation and splicing. The RNA may exit to the cytoplasm through the nuclear pore complex; the stretch of DNA transcribed into an RNA molecule is called a transcription unit and encodes at least one gene.
If the gene encodes a protein, the transcription produces messenger RNA. Alternatively, the transcribed gene may encode for non-coding RNA such as microRNA, ribosomal RNA, transfer RNA, or enzymatic RNA molecules called ribozymes. Overall, RNA helps synthesize and process proteins. In virology, the term may be used when referring to mRNA synthesis from an RNA molecule. For instance, the genome of a negative-sense single-stranded RNA virus may be template for a positive-sense single-stranded RNA; this is because the positive-sense strand contains the information needed to translate the viral proteins for viral replication afterwards. This process is catalyzed by a viral RNA replicase. A DNA transcription unit encoding for a protein may contain both a coding sequence, which will be translated into the protein, regulatory sequences, which direct and regulate the synthesis of that protein; the regulatory sequence before the coding sequence is called the five prime untranslated region. As opposed to DNA replication, transcription results in an RNA complement that includes the nucleotide uracil in all instances where thymine would have occurred in a DNA complement.
Only one of the two DNA strands serve as a template for transcription. The antisense strand of DNA is read by RNA polymerase from the 3' end to the 5' end during transcription; the complementary RNA is created in the opposite direction, in the 5' → 3' direction, matching the sequence of the sense strand with the exception of switching uracil for thymine. This directionality is because RNA polymerase can only add nucleotides to the 3' end of the growing mRNA chain; this use of only the 3' → 5' DNA strand eliminates the need for the Okazaki fragments that are seen in DNA replication. This removes the need for an RNA primer to initiate RNA synthesis, as is the case in DNA replication; the non-template strand of DNA is called the coding strand, because its sequence is the same as the newly created RNA transcript. This is the strand, used by convention when presenting a DNA sequence. Transcription has some proofreading mechanisms, but they are fewer and less effective than the controls for copying DNA.
As a result, transcription has a lower copying fidelity than DNA replication. Transcription is divided into initiation, promoter escape and termination. Transcription begins with the binding of RNA polymerase, together with one or more general transcription factors, to a specific DNA sequence referred to as a "promoter" to form an RNA polymerase-promoter "closed complex". In the "closed complex" the promoter DNA is still double-stranded. RNA polymerase, assisted by one or more general transcription factors unwinds 14 base pairs of DNA to form an RNA polymerase-promoter "open complex". In the "open complex" the promoter DNA is unwound and single-stranded; the exposed, single-stranded DNA is referred to as the "transcription bubble."RNA polymerase, assisted by one or more general transcription factors selects a transcription start site in the transcription bubble, binds to an initiating NTP and an extending NTP complementary to the transcription start site sequence, catalyzes bond formation to yield an initial RNA product.
In bacteria, RNA polymerase holoenzyme consists of five subunits: 2 α subunits, 1 β subunit, 1 β' subunit, 1 ω subunit. In bacteria, there is one general RNA transcription factor: sigma. RNA polymerase core enzyme binds to the bacterial general transcription factor sigma to form RNA polymerase holoenzyme and binds to a promoter. In archaea and eukaryotes, RNA polymerase contains subunits homologous to each of the five RNA polymerase subunits in bacteria and contains additional subunits. In archaea and eukaryotes, the functions of the bacterial general transcription factor sigma are performed by multiple general transcription factors that work together. In archaea, there ar
Forensic science is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal procedure. Forensic scientists collect and analyze scientific evidence during the course of an investigation. While some forensic scientists travel to the scene of the crime to collect the evidence themselves, others occupy a laboratory role, performing analysis on objects brought to them by other individuals. In addition to their laboratory role, forensic scientists testify as expert witnesses in both criminal and civil cases and can work for either the prosecution or the defense. While any field could technically be forensic, certain sections have developed over time to encompass the majority of forensically related cases. Forensic science is a combination of two different Latin words: science; the former, relates to a discussion or examination performed in public. Because trials in the ancient world were held in public, it carries a strong judicial connotation.
The second is science, derived from the Latin word for ‘knowledge’ and is today tied to the scientific method, a systematic way of acquiring knowledge. Taken together forensic science can be seen as the use of the scientific methods and processes in crime solving; the word forensic comes from the Latin term forensis, meaning "of or before the forum". The history of the term originates from Roman times, during which a criminal charge meant presenting the case before a group of public individuals in the forum. Both the person accused of the crime and the accuser would give speeches based on their sides of the story; the case would be decided in favor of the individual with delivery. This origin is the source of the two modern usages of the word forensic – as a form of legal evidence and as a category of public presentation. In modern use, the term forensics in the place of forensic science can be considered correct, as the term forensic is a synonym for legal or related to courts. However, the term is now so associated with the scientific field that many dictionaries include the meaning that equates the word forensics with forensic science.
The ancient world lacked standardized forensic practices, which aided criminals in escaping punishment. Criminal investigations and trials relied on forced confessions and witness testimony. However, ancient sources do contain several accounts of techniques that foreshadow concepts in forensic science that were developed centuries later; the first written account of using medicine and entomology to solve criminal cases is attributed to the book of Xi Yuan Lu, written in China by Song Ci in 1248, a director of justice and supervision, during the Song dynasty. Gunhegarancha Kardankal authored by Dr. Vasudha Apte in Marathi provides information about 130 different methods of forensic investigations in detail. Song Ci ruled regulation about autopsy report for court, how to protect the evidence in the examining process, the reason why workers must show examination to public impartiality, he concluded methods on how to make antiseptic and to reappear the hidden injury from dead bodies and bones. At that time, the book had given methods to distinguish pretending suicide.
In one of Song Ci's accounts, the case of a person murdered with a sickle was solved by an investigator who instructed everyone to bring his sickle to one location. Flies, attracted by the smell of blood gathered on a single sickle. In light of this, the murderer confessed. For example, the book described how to distinguish between a drowning and strangulation, along with other evidence from examining corpses on determining if a death was caused by murder, suicide or an accident. Methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the Polygraph test. In ancient India, some suspects were made to spit it back out. In ancient China, those accused of a crime would have rice powder placed in their mouths. In ancient middle-eastern cultures, the accused were made to lick hot metal rods briefly, it is thought that these tests had some validity since a guilty person would produce less saliva and thus have a drier mouth.
In 16th-century Europe, medical practitioners in army and university settings began to gather information on the cause and manner of death. Ambroise Paré, a French army surgeon, systematically studied the effects of violent death on internal organs. Two Italian surgeons, Fortunato Fidelis and Paolo Zacchia, laid the foundation of modern pathology by studying changes that occurred in the structure of the body as the result of disease. In the late 18th century, writings on these topics began to appear; these included A Treatise on Forensic Medicine and Public Health by the French physician Francois Immanuele Fodéré and The Complete System of Police Medicine by the German medical expert Johann Peter Frank. As the rational values of the Enlightenment era increasingly