210 THE ACUTE PNEUMONIAS 



bouillon cultures with alcohol or ammonium sulphate, and 

 poisonous effects have been produced by certain substances thus 

 derived ; but the effects produced are, as in so many other 

 similar cases, of a non-specific character and to be classed as 

 interferences with general metabolism. The general conclusion 

 has been that the toxins at work in pneumonia are intracellular ; 

 but no special light has been thrown on the common effects of 

 the members of this group of bacterial poisons. 



Immunisation against the Pneumococcus. Animals can be 

 immunised against the pneumococcus by inoculation with 

 cultures which have become attenuated by growth on artificial 

 media, or with the naturally attenuated cocci which occur in the 

 sputum after the crisis of the disease. Netter effected immun- 

 isation by injecting an emulsion of the dried spleen of an animal 

 dead of pneumococcus septicaemia. Virulent cultures killed by 

 heating at 62 C., rusty sputum kept at 60 C. for one to two 

 hours and then filtered, and filtered or unfiltered bouillon 

 cultures similarly treated have also been used. In all cases one 

 or two injections, at intervals of several days, are sufficient for 

 immunisation, but the immunity has often been observed to 

 be of a fleeting character and may not last more than a few 

 weeks. The serum of such immunised animals protects rabbits 

 against subsequent inoculation with pneumococci, and if injected 

 within twenty-four hours after inoculation, prevents death. A 

 protective serum was obtained by Washbourn, who employed 

 pneumococcus cultures of constant virulence. This observer 

 immunised a pony by using successively (1) broth cultures killed 

 by one hour's exposure to 60 C. ; (2) living agar cultures ; (3) 

 living broth cultures. From this animal there was obtained a 

 serum which protected ' susceptible animals against many times 

 an otherwise fatal dose, and which also had a limited curative 

 action. It is stated that the serum of patients who have 

 recovered from pneumonia has in a certain proportion of cases 

 a protective effect against the pneumococcus in rabbits, similar 

 to that exhibited by the serum of immune animals. 



The Klemperers treated a certain number of cases of human 

 pneumonia by serum derived from immune animals, and appar- 

 ently with a certain measure of success, and sera prepared by 

 Washbourn and by others have also been used. The results 

 obtained by different observers have, however, been rather con- 

 tradictory. The use of these sera apparently causes the tempera- 

 ture in some cases to fall, and even may hasten a crisis, but 

 further experience is necessary before their value in therapeutics 

 can be properly estimated. 



