Biological Reactions

Biological Reactions, methods of qualitative and quantitative determination of physiological and pharmacological substances based on their action on living organisms. Some B. r. are highly sensitive and are used when the amount of material to be analyzed is too small for chemical research. B. r. are widely used in pharmaceutical laboratories for standardizing preparations of internal secretory glands, cardiac agents, etc. The test is performed on both whole animals and isolated organs (uterus, intestine, heart, ear, etc.); for some poisons, the measure of quantity is considered a conditional 'biological unit,' for example, the 'rabbit unit,' established by the Toronto laboratory for standardizing insulin (that amount of preparation which in a rabbit weighing 2 kg lowers the blood sugar content to 0.045%). An example of B. r. can be the determination of adrenaline according to Shimidzu (Shimidzu, 1924); the indicator is the rabbit's eye; the concentration of the adrenaline solution being tested is judged by the degree of pupil dilation, examined under a microscope with a micrometer eyepiece. This method makes it possible to detect adrenaline in concentrations of 1:10,000,000. Sources of error in the production of B. r. can be the individual peculiarities of sensitivity of the animal taken for the test.