240 ' THE ACUTE PNEUMONIAS 



interference with the heat-regulating mechanism, and from 

 general nervous depression that death usually results. These 

 considerations, taken in connection with the fact that in man 

 the organisms are found in the greatest numbers in the lung, 

 suggest that a toxic action is at work. Various attempts have 

 been made to isolate toxins having specific effects, but these have 

 been unsuccessful. The general conclusion has been that the 

 toxins at work in pneumonia are intracellular ; as in other cases, 

 we may have to reckon with the distribution in the infected 

 body of poisonous substances consequent on lysis of the infective 

 agent. While the chief multiplication of the pneumococcus in 

 pneumonia occurs in the lung, the organism frequently is found 

 in the blood, and according to some observers its presence in 

 greater numbers than 15 cocci per c.c. is of fatal import. 



There has been considerable difference of opinion as to the 

 explanations to be given of the facts observed regarding im- 

 munisation against the pneumococcus, and especially regarding 

 the protective and curative properties of immune sera. There is 

 no evidence that such sera possess either antitoxic or bactericidal 

 properties. Within recent times many have accordingly turned 

 to the opsonic property of sera to account for the facts observed. 

 In this connection Mennes observed that normal leucocytes 

 only become phagocytic towards pneumococci when they are 

 lying in the serum of an animal immunised against this 

 bacterium. Wright instanced the pneumococcus as an organism 

 insensible to bactericidal action but very sensitive to opsonins, 

 and Neufeld and Eimpau have described the occurrence of an 

 opsonic — or, as they called it, a bacteriotropic — -effect in the 

 action of an anti-pneumococcic serum. 



In studying further the relationship of the opsonic effect to 

 pneumococcic infection, inquiry has been directed to the opsonic 

 qualities, of the blood of pneumonic patients, especially with a 

 view to throwing light on the nature of the febrile crisis, the 

 essential nature of which is, however, still entirely obscure. 

 According to some results, the opsonic index as compared with 

 that of a healthy person is not above normal, but if the possible 

 phagocytic capacities of the whole blood of the sick person be 

 taken into account, these may be above normal in consequence 

 of the leukocytosis which usually accompanies a successful re- 

 sistance to this infection. It has been observed, however, that 

 as the crisis approaches in a case which is to recover, the 

 opsonic index rises, and after defervescence gradually falls to 

 normal. Correlated with this, there has been observed about 

 the crisis an increase in the serum of substances capable of 



