PNEUMONIA. 285 



011s exudate resembling somewhat that in diphtheria. 

 At times, and especially in dogs, there may be a little 

 pus formed. The other appearances are those of a 

 general disturbance. The spleen is much enlarged, is 

 firm and red brown. The blood in all the organs contains 

 large numbers of the bacteria, most of which exhibit a 

 distinct lanceolate form and have their capsules very 

 distinct. The disease is a pure septicemia unassociated 

 with pronounced tissue-changes. 



In cases of the kind described the lungs show no pneu- 

 monic changes. Likewise, if the hypodermic needle 

 used for injection be plunged through the breast-wall 

 into the pulmonary tissue, no pneumonia results. Mon- 

 ti, however, claims to have found that a true character- 

 istic pneumonia results from the injection of cultures 

 into the trachea of susceptible animals. This observa- 

 tion lacks confirmation. 



Not all animals are susceptible. Guinea-pigs, mice, 

 and rabbits are highly sensitive to the operations of the 

 organism ; dogs are comparatively immune. 



From this brief review of the peculiarities of the pneu- 

 mococcus it must be obvious that its reputation in pneu- 

 monia depends more upon the regularity with which it is 

 found in that disease than upon its capacity to produce a 

 similar affection in the lower animals. 



As in numerous other diseases, we are unable to furnish 

 an absolute proof of specificity according to the postu- 

 lates of Koch. 



The disease is peculiar in that recovery from it is fol- 

 lowed either by no immunity or by one of such brief dura- 

 tion as to allow of frequent relapses ; and it is well known 

 that many cases show a subsequent predisposition to 

 fresh attacks of the disease. This brevity of immunity 

 lessens the probability that in the future we shall dis- 

 cover an antitoxin that shall be powerful in its influ- 

 ence upon the course and termination of the disease. 



The experiments of G. and F. Klemperer, 1 a few years 



1 Berliner klin. Wochenschrift, 1891, No>. 34 and 35. 



