162 VETERINARY BACTERIOLOGY 



tion, or the injection of dead or living bacteria into the body, with 

 the resultant development of an active immunity, owes its effi- 

 ciency, in some cases at least, to the production, by the body, of the 

 bacteriolysins specific for the organism. 



Bacteriolytic sera for passive immunization are not employed 

 against many diseases. Some organisms, as has been stated, cause 

 the production of little or no bacteriolysin. The bacteriolysin 

 developed in the blood of one species is not always suitable for the 

 passive immunization of another. There "have been various 

 reasons advanced for this fact: the injection of the foreign serum 

 may cause the production of anti-amboceptors, or of anticom- 

 plements, or of some other antibody which would inhibit the lytic 

 action of the injected serum. Complement soon disappears from 

 an immune serum; therefore the amboceptors are dependent for 

 their activation upon the normal complement of the blood. This 

 complement may not in all cases be suitable for combination with 

 the particular amboceptor used, and the lytic activity be thus 

 inhibited. When the antiserum to be used for passive immuni- 

 zation comes from the same species of animal, as is the case in 

 immunization against hog-cholera and rinderpest, these objections 

 do not seem to obtain. 



Hemolysins. Hemolysins for the red blood-cells of one animal 

 usually may be obtained by injection of these into another. 

 They are divided into three types, the classification being made 

 upon the basis of relationship. Heterolysins are developed by the 

 injection of the red blood-cells of one species into another; isolysins 

 by the red blood-cells of one animal into another animal of the same 

 species, and autolysins by an individual for his own red blood-cells. 

 The last two, particularly the autolysins, are not easily produced 

 or demonstrated. 



The study of hemolysis has proved of great value in two ways: 

 First, hemolysis is a phenomenon that may be easily observed, 

 and it has been used, therefore, more than any other, in the study 

 of the nature and activity of cytolysins. Hemolysis is readily 

 detected, because the hemoglobin escapes into the solution and it 

 remains permanently red, while unhemolyzed red blood-corpuscles 

 soon sink to the bottom, leaving the blood-serum clear and color- 

 less. Second, they are made of indirect use in the diagnosis of 



