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. S. Weir Mitchell first disproved this hypothesis through the ex- 

 perimental basis and estabhshed the chemical nature of the fatal principles 

 of snake venom. Lucien Bonaparte recognized a httle 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. 



Ehrhch, 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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