Post-Infections Immunity. 27 



cause a flocculent precipitate. Init which will not (as a rule, and 

 never if certain m(3des of application are employed) exhibit such 

 precipitating^ qualities with any other type of blood. It is inter- 

 esting in this connection to add that the serum of a rabbit so 

 treated will also precipitate the blood of anthropoid apes, gorillas, 

 orang-outangs and chimpanzees, thus indicating a relationship of 

 these animals to man. Cytolysins and haemolysins also serve to 

 show the relationships existing between animals in the zoological 

 system of classification. Inasmuch as this reaction is applicable 

 as well with a solution of old and dried blood, the discovery 

 (which as an outcome of research in the field of immunity is due 

 particularly to Bordet, Ehrlich and Morgenroth) has acquired 

 especial importance as a means of information concerning the 

 source of blood stains in forensic medicine. 



Other albumens may also lead to the formation of specific 

 antibodies in the animal organism, as milk albumen ; thus by 

 subcutaneous injection of goat's milk into rabbits, horses or cows 

 a serum may be obtained which wilt immediately cause a precipi- 

 tate if it be added to goat's milk. In the same way, by inocula- 

 tion, coagulins may be obtained for cow's milk. 



In the same way, too, in the course of an infectious disease 

 a series of substances are produced in the human or ani- 

 mal organism which render the infectious matter for the time 

 harmless. Should the infectious products develop very rapidly, 

 and by their poisonous properties cause serious protoplasmic 

 changes in the bodv cells, the disturbance is apt not to be limited 

 or checked, and in spite of any reactive-products which may be 

 formed the function of the cells becomes altered and the animal 

 dies. Should the [protoplasmic molecules of these] cells be only 

 partly injured the body prevails over the disease, the molecular 

 defects of the cells becoming regenerated. The surplus of anti- 

 bodies, the result of this regenerative action, are after recovery 

 found circulating in the blood, and in some instances may even 

 pass into the milk. The amount of protective bodies or anti- 

 bodies in the body-fluids varies according to the intensitv of the 

 reaction and the time elapsed after recovery from the infection, 

 the greater part being used up during the course of the disease 

 and the remaining gradually disappearing in metabolism ; while 

 with the removal of the stimulus the supply from the cells tends 

 to cease. If, however, infectious and toxic material be again 

 introduced into the system, stimulating and injuring the cellular 



