Physiology
Physiology is the study of how various biological components work independently and together to enable organisms, from animals to microbes, to function. This scientific discipline covers a wide variety of functions from the cellular and sub-cellular level to the interaction of organ systems that keep the complex biological machines of humans running.
Because a forensic examination involving an injury or death is often concerned with establishing cause, a forensic investigator will of necessity be concerned with physiology. By understanding the proper functioning of organs and organ systems, a forensic investigator is able to recognize abnormalities. Moreover, the nature of an abnormality can provide clues as to the nature of its cause.
For example, if a person experienced a rapid onset of paralysis prior to their death, the investigator might suspect the involvement of the toxin produced by the bacterium Clostridium botulinum. Appropriately, nervous tissue and blood would be examined for the presence of the toxin.
More generally, physiological studies are aimed at answering many other questions in addition to forensic questions. Physiologists investigate topics ranging from precise molecular studies of how food is digested to more general studies of how thought processes relate to electrical and biochemical patterns found in the brain (a branch of this discipline known as neurophysiology). It is often physiology-related investigations that uncover the origins of diseases.
While physiological studies are one of the cutting-edge tools in a forensic examination, the roots of the discipline date back to at least 420 B.C. and the time of Hippocrates. More refined physiological approaches first appeared in the seventeenth century when scientific methods of observation and experimentation were used to study blood movement, or circulation, in the body. In 1929, American physiologist W. B. Cannon coined the term homeostasis to describe how the varied components of living things adjust to maintain a constant internal environment conducive to optimal functioning. Proper physiology relies on homeostasis.
Homoestasis is an important aspect of forensic science. A specific disturbance to the body caused by, for example, a poison such as a toxin can have other effects (e.g., loss of muscle control, difficulty breathing, mental confusion) as the body is more generally affected.
Physiological studies have evolved from the first visual-based methods to now encompass a variety of analytical procedures. The use of analytical instruments such as the gas chromatograph, electrophoretic techniques that can detect and identify components such as toxins, the elemental analytical power of mass spectroscopy, and various other techniques have made forensic physiological determinations highly sensitive and specific.