RECOVERY. 511 



cus which was virulent for rabbits under his skin 

 without suffering more than temporary disturb- 

 ance. 



Eecovery seems to indicate an acquired immun- Recovery. 

 ity or resistance which is by no means permanent, 

 and often is of very short duration. One may have 

 as many as eight or ten attacks of pneumonia, the 

 intervals between attacks being from three to five 

 years on the average (Griswolle). What the re- 

 covery or acquired resistance depends on is a mat- 

 ter of much discussion. 



Neufeld and Haendel believe that the antibodies 

 in pneumonia are inactive until a certain concen- 

 tration is reached and that when a high enough 

 development of antibodies occurs, there is a sudden 

 neutralization of toxins with destruction of pneu- 

 mococci leading to the crisis. These authors find 

 that the serum of patients, who have passed the 

 crisis, is protective for mice against many fatal 

 doses of pneumococci. Other observers have failed 

 to find any evidence that the crisis is due to anti- 

 body production. The marked leucocytosis of 

 pneumonia, and the known phagocytic power of 

 the leucocytes for the diplococcus, suggest strongly 

 the importance of the leucocytes for recovery. The 

 serums of convalescents and of immune animals 

 show no increased bactericidal power for the 

 organism, nor are they strikingly antitoxic. The 

 opsonic power of the serum in pneumonia is 

 decreased in the early stages of the disease and 

 reaches its height at the crisis and the following 

 few days. 



Some of the serums which have been prepared serotherapy 



, T ,T ,. ,, ,1 and A 



have been used therapeutically in man, but the re- ation. 

 suits have not been sufficiently satisfactory to put 



