IMMUNITY AND PROTECTIVE INOCULATION 509 
solvent action for erythrocytes of species B, and only for this species. 
(There are a few exceptions to this general rule). We call this 
hemolysis, and the substances which affect the solution of the red cells, 
hemolysins or hemotoxins.”’ 
Bordet has been able to show that the solvent power of the specific hemolysins 
depended on the combined action of two constituents of the specific serum. Thus, 
when the fresh hemolytic serum was heated for a half hour at 55° C. it lost its power. 
If to this inactive serum a very small amount of the serum of a normal guinea pig 
was added, the full hemolytic power was restored to this inactive serum. In other 
words, it had been reactivated by this addition. This experiment showed that the 
hemolytic action of the specific hemolytic serum depends upon two substances: (1) the 
one destroyed by heating to'55° C. and which is contained in the serum of the normal 
untreated animal as well as in the specific hemolytic serum, and (2) a substance that 
is able to withstand heating to 55° C. and which is contained in the specific serum only. 
The substance which is destroyed at 55° C. and which exists in the blood of the 
untreated animal and in the specific serum constitutes the alexins of Buchner. The 
substance which is not destroyed by heating to 55° C. and which is brought about by 
the action of the blood of one species upon another is known as the immune body, or 
as termed by Buchner substance sensibilatrice. 
Agglutinating power of hemolytic serum. It was found by Bordet 
that another property was increased in the hemolytic serum, namely, 
the power of clumping red blood corpuscles. This clumping or 
so-called agglutination of the red cells occurs previous to their solution. 
This action Bordet considers as a specific one. Wassermann has 
formulated this reaction thus: “If an animal, species A, be treated with 
blood of species B, the serum derived from A will have acquired an 
agglutinating power which differs from that of normal serum of A in 
one very important particular, namely, in that it is specifically increased 
with respect to the red cells of species B or its nearest biological rela- 
tive. This clumping must not be confounded with rouleaux forma- 
tion in normal blood.” 
For a more extended discussion of the subject of hemolysis and for 
cytolysis, cytotoxins agglutinins and precipitins the student is 
referred to the special literature on these subjects. 
Protective inoculation. The practical application of immunity in 
protective inoculations or vaccination has come to mean the establish- 
ment of partial or complete immunity in the individual against the 
disease in question. The vaccination against small pox introduced 
by Jenner in 1796 is a well known example of protective inoculation. 
Following the work of Pasteur there developed many procedures 
for establishing both active and passive immunity against a number 
