74 



IMMUNE SERA 



ence between a specific haemolytic or bactericidal 

 serum and a normal one, we must first of all study 

 the behavior of normal serum toward alien red 

 cells and bacteria. It has long been known to 

 physiologists that fresh normal serum of many 

 animals has the power to dissolve blood cells of 

 another species. This was studied especially by 

 Landois. One-half to one c.c. of normal goat serum, 

 for example, is able to dissolve 5 c.c. of a 5% mix- 

 ture (in normal salt solution) of rabbit or guinea 

 pig red cells. In the same way, these red cells 

 are dissolved by the sera of oxen, of dogs, etc. 

 This normal globulicidal property of the serum cor- 

 responds to another which fresh normal serum was 

 found to possess, namely, the property to dissolve 

 appreciable quantities of many species of bacteria. 

 This analogy was pointed out by Fodor, Nutall, 

 Nissen, and especially by Buchner. We call this 

 the bactericidal property of fresh normal serum. 



This property is well illustrated by the following 

 protocol from Park. 



It is at once apparent that the number of bacteria 

 introduced is an important factor, the normal serum 

 being able to kill off only a certain number. 



