146 CLINICAL BACTERIOLOGY. 



tarily in the search for pleuritic effusions (exploratory 

 puncture) without ever doing any harm. 



If the information be sought whether the pneumococcus 

 participates in the process, it is best to inject subcuta- 

 neously some of the sputum or pulmonary fluid into a mouse, 

 or, better, into the still more susceptible rabbit. If the 

 pneumococcus is present, the animal will die in from twenty- 

 four to forty-eight hours in consequence of diplococcus- 

 septicemia, which is readily demonstrable microscopically 

 in stained cover-glass preparations from the heart's blood 

 of the animal. 



Prognostic significance is to be attached in only limited 

 degree to the results of bacteriologic examination, be- 

 cause in the case of pneumonia also much depends upon 

 the virulence of the exciting agent. However, a crisis may 

 be looked for with greater assurance when pneumococci 

 alone are found than under any other conditions. It must, 

 however, not be forgotten that even in cases of pure pneu- 

 mococcus-pneumonia the crisis may not occur ; while, on 

 the other hand, it may be present in cases of streptococcus- 

 pneumonia. The general condition of the patient, evidently, 

 is of considerable importance in this connection, and it 

 must be given due consideration in every aspect in pre- 

 dicting the crisis. Thus, the prognosis is unfavorable in 

 the pneumonia of alcoholics, in that of the aged, and of 

 those with kyphosis, even when pneumococci alone are 

 found. The patients often die before the crisis, or the dis- 

 ease pursues a protracted course, and terminates late with- 

 out the occurrence of a crisis. The pneumococcus-pneu- 

 monia of tuberculous subjects justifies a more favorable 

 prognosis than a purely tuberculous pneumonia under the 

 same conditions. 



Reference has already been made to the conception of 

 the crisis as indicating the advent of immunity, as well as 

 to the evidence of the immunizing property of the blood- 

 serum after the crisis in a number of cases of pneumonia. 

 Why this immunity is so transient, disappearing in some 

 cases in the course of a few days, is not yet known. In 

 any event it has been established clinically that pneumonia 

 has a tendency to recur, and it may almost be included 

 among those diseases of which one attack rather predisposes 

 to subsequent attack. In a pneumococcus-culture the 

 bacteria die in the course of a few days (from four to seven), 



