PHENOMENA FOLLOWING IMMUNIZATION 91 



this depended on specific constituents of the immune serum which 

 rendered the bacteria more amenable to the phagocytic action of the 

 cells. These further antibodies we will discuss in a subsequent chap- 

 ter, under the terms "opsonins" and "bacteriotropins," designations 

 applied to them by their discoverers. 



We have thus reviewed briefly the various specific properties 

 which develop in the serum of an animal when it is systematically 

 treated (actively immunized) with bacteria or bacterial products. 

 These serum activities have been attributed to the development in 

 the serum of substances which we speak of as "antibodies." 



In our discussion of the first of these antibodies, antitoxin, we 

 call attention to the fact that the principle discovered in the case of 

 bacterial toxins was rapidly extended to vegetable poisons, snake 

 venom, spider poison and enzymes. It was found that the power of 

 inciting antitoxins when injected into animals was an attribute be- 

 longing to a large group of substances in nature, and not limited to 

 bacteria alone. A similar generalization of conception has been pos- 

 sible with other antibodies. Specific lysins, agglutinins, and pre- 

 cipitins may be produced by the treatment of animals with many 

 substances not of bacterial nature. 



The first observation of this kind was made almost simultaneously 

 by Bordet 43 and by Belfanti and Carbone. 44 They observed that 

 the serum of an animal that had been treated with the red cells of 

 another species acquired the power of laking these cells. That the 

 normal serum of one species is often toxic to, and causes the laking 

 of, the erythrocytes of another species is an observation that dates 

 back to the earliest experiments on transfusion, and had been studied 

 in considerable detail by Landois as early as 1875. The phenom- 

 enon possesses much interest in its bearing on the problems of ana- 

 phylaxis and will be discussed more particularly in that connection. 

 We mention it in this place to show that, like bactericidal bodies, 

 "hemolytic" (erythrocyte laking) properties may be present in nor- 

 mal sera, though irregularly and by no means occurring in every 

 species of animal. Incidentally it may be stated that this is true 

 also of agglutinins and of opsonins which may be found in consider- 

 able amounts in normal sera. Of precipitins, however, this does not 

 seem to be true. 



By the work of Bordet it was found that "hemolysins" could be 

 specifically 45 incited in an animal by systematically treating it with 



43 Bordet. Ann. Past., Vol. 12, 1898. 



44 Belfanti and Carbone. Giorn. della R. Acad. di Torino, July, 1898. 



45 By the use of the word specific in this case we imply that an animal 

 immunized with any given variety of red blood cells will form hemolysins 

 for this variety only. Thus an animal treated with ox blood will form ox 

 blood hemolysins only, and his serum, though strongly hemolytic for ox 

 blood, will not lake sheep cells, dog cells, human cells, etc. 



