PNEUMONIA 415 



4. That the pathogenic activities of the pneumococcus are 

 not referable to an extracellular toxin, properly so called, 

 but rather to an endotoxic component that is liberated 

 in the body when the bacteria are disintegrated and that 

 may be liberated artificially by certain solvents and under 

 such conditions as favor autolysis, i. e., self-digestion of 

 the bacteria. 



5. That in the blood of convalescents from pneumonia 

 specific, protective antibodies are to be found, but as they 

 are inconstant both as to their presence and as to their 

 amounts it is impossible to decide their role in the mechanism 

 of recovery. 



6. That animals may be actively immunized from pneu- 

 mococcus infection with but little difficulty, but the serum 

 from such animals is not always of value in either preventing 

 infection in other animals in which it is injected or of miti- 

 gating or curing infections already established in animals. 



It is only by keeping in mind the foregoing facts that we 

 are able to appreciate the difficulties surrounding the problem 

 of pneumonia or to properly estimate the value of certain 

 important experimental results having a bearing upon it; 

 notwithstanding the light already thrown on the subject 

 by the discovery of various types of the causative organism 

 and the development of knowledge upon their several pecu- 

 liarities. 



Given a group of persons with either of the established 

 types of pneumococci in their mouths, noses and pharynges, 

 why is it that some may develop pneumonia and others 

 remain in health? 



It has been customary to reply: that in those developing 

 the disease there has been a lessening of the general vitality 



