PNE UMONIAIMM UNIZA TION 419 



robbing them of their power to produce infection when 

 removed alive from the pneumonic patient. 



It also has been suggested that the crisis constitutes the 

 advent of a refractory state on the part of the tissues a 

 state having some analogies to anaphylactic shock. As 

 yet this can be taken only as a suggestion. Much more in 

 the way of experimental evidence is needed before it can 

 be accepted. 



It is scarcely suitable to a book of this character to pursue 

 all the lines of argument that have been advanced in con- 

 nection with this subject. It suffices to say that at present 

 we are forced still to speculate as to the nature of at least 

 some of the important factors responsible for the self limi- 

 tation of this desease. 



Immunization and Specific Antisera. Little difficulty has 

 been experienced in the efforts to actively immunize animals 

 from pneumococcus infection. Horses have been carried 

 to such a high degree of immunization by repeated intra- 

 venous injection of pneumococcus cultures that as much as 

 2500 c.c. of a virulent culture has been injected into the 

 veins at one time. 



From such highly immunized animals sera have been 

 obtained of remarkable potency in preventing infection; 

 thus Cole found that 0.2 c.c. of serum from one of his 

 immunized horses would protect a mouse from a million- 

 fold the lethal dose of virulent pneumococci, provided the 

 serum and the culture be injected into the animal at the 

 same time. But if the animal be first infected, then the 

 serum has practically no saving powers even though it be 

 injected only a few hours later and in very much larger 

 amounts; in fact, Cole states, it is difficult or impossible 

 to rescue the animal, no matter how much serum is injected. 



