PRINCIPLES OF VETERINARY SURGERY 169 



takes up the phenomena of "lysis." These phenomena in- 

 volve not only the dissolution (lysis) of bacteria, but also of 

 other cells. Three general lysins are named : 



1. Bacteriolysins, — those which dissolve bacteria. 



2. Hemolysins, — those which dissolve red blood cor- 

 puscles. 



3. Cytolysins, — those which dissolve other cells, such 

 as spermatozoa, etc. 



The practical application of all the lysins is discussed 

 under a special heading. We shall now take up the con- 

 stitution and action of those which are involved in anti- 

 bacterial immunity. They are the same in structure as 

 the hjemoiysins and cytolysins, and the action of all is 

 similar. 



It was Pfeififer who discovered that a cavy which, has 

 been immunized to cholera vibrios will dissolve them if 

 they be injected into the peritoneal ca\'ity. The freshly 

 drawn serum of the animal also possesses the same power, 

 but loses it if heated to 55" C, or if it stands for some 

 eight or ten days. But if this heated or old serum be in- 

 jected into the peritoneal cavity, or blood of, another guinea- 

 pig, or of any animal, or if any fresh serum or blood be added 

 to it in a test-tube, its bactericidal property is restored, and 

 it will again destroy the bacilli. From these observations 

 the fact has become gradually apparent that there are two 

 vital principles in a bactericidal serum : one which is re- 

 sistant to heat and is produced by the immunization of an 

 animal to cholera bacilli, and one which is sensitive to heat 

 and is present in the healthy normal serum of every animal. 

 Ehrlich designates these two substances as immune body 

 and complement. The immune body he considers to origi- 

 nate the same as the antitoxin from the receptors of the 

 cells. Inasmuch as it cannot destroy the bacteria alone, 

 but can when the complement is present, he represents its 



