INTRODUCTORY. 
At a certain stage of the evolution of our modern knowledge of snake 
venom the action of the venom was attributed to the presence of microscopi- 
cal animalcules in the poison. According to this theory the animalcules, 
introduced through the bite of the snake, multiply rapidly and bring about 
death. Dr. 5S. Weir Mitchell first disproved this hypothesis through the ex- 
perimental basis and established the chemical nature of the fatal principles 
of snake venom. Lucien Bonaparte recognized a little earlier the protein 
nature of the venom and called the toxic constituent echidnin, while Dr. 
Mitchell gave the term crotaline to the active principles of rattlesnake venom. 
While Bonaparte failed to overthrow the germ theory, Mitchell succeeded in 
doing so, and finally, in his further pursuit of the subject, so thoroughly 
cleared up the chemistry of snake poisons that the analysis made by him and 
his associate Reichert, in 1886, stands to-day with but little modification by 
later investigators. ‘The exhaustive and extensive investigations of Mitchell 
and Reichert taught us that snake venom is no simple substance, but consists 
of several different active principles, each with its characteristic properties; 
that these toxic principles are of a proteid nature and can be separated into 
three main groups: globulins, venom peptone, and venom albumen, the latter 
being without poisonous property. 
While the work above referred to revealed for the first time the complex 
nature of snake venom, a little over a score of years has since passed and in 
the meanwhile our knowledge of venom has greatly increased, especially 
through the influence of biological methods of study. 
While Mitchell, Fayrer, Brunton, Lacerda, Calmette, and others were 
actively engaged with the researches upon venom, modern microbiology was 
inaugurated by Pasteur and Robert Koch, and through the efforts of their 
followers immunology and toxinology have been instituted. 
Ehrlich, Behring, Roux, Kitasato, Brieger, Metchnikoff, and their pupils 
have demonstrated by their investigations the existence of a group of sub- 
stances whose characteristics are thermolability, chemiolability, toxicity 
and unknown chemical constitution, and, above all, their capability to stimu- 
late in the animal body the formation of specific antisubstances. These 
substances are known as toxins and are elaborated by the activity of animal 
as well as plant cells. Bacteria often produce powerful toxins, but many 
toxin-like substances are produced in the higher plants. Thus, Rudolph 
Kobert and his pupils, notably Stillmark, studied carefully the properties of 
the®active toxic principle, ricin, of the castor bean, Ricinus communis. The 
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