290 BACTERIA IN CROUPOUS PNEUMONIA. 



nature of this disease is due to its presence in the fibrinous exudate into the 

 pulmonary alveoli. 



" But this cannot be considered as definitely established by the experi- 

 ments which have thus far been made upon the lower animals. The con- 

 stant ' presence of this micrococcus in the buccal secretions of healthy per- 

 sons indicates that some other factor is required for the development of an 

 attack of pneumonia ; and it seems probable that this other factor acts by re- 

 ducing the vital resisting power of the pulmonary tissues, and thus making 

 them vulnerable to the attacks of the microbe. This supposition enables vis 

 to account for the development of the numerous cases of pneumonia which 

 cannot be traced to infection from without. The germ being always pre- 

 sent, auto-infection is liable to occur when, from alcoholism, sewer-gas 

 poisoning, crowd poisoning, or any other depressing agency, the vitality of 

 the tissues is reduced below the resisting point. We may suppose, also, that 

 a reflex vaso-motor paralysis, affecting a single lobe of the lung, for exam- 

 ple, and induced by exposure to cold, may so reduce the resisting power of 

 the pulmonary tissue as to permit this micrococcus to produce its character- 

 istic effects. 



"Again, we may suppose that a person whose vital resisting power is 

 reduced by any of the causes mentioned may be attacked by pneumonia 

 from external infection with material containing a pathogenic variety of 

 this micrococcus having a potency, permanent or acquired, greater than that 

 possessed by the same organism in normal buccal secretions." 



This is the theory by which I have attempted to explain the etiological 

 role of this micrococcus in croupous pneumonia. Let us now consider the 

 principal facts which have led to a belief in its causal relation to this disease. 



Friedlander, in 1882, observed, in eight fatal cases of pneumonia in which 

 he made autopsies, microorganisms, having an oval form, in the exudate into 

 the pulmonary alveoli; they were in pairs or in short chains. Without af- 

 firming that this microorganism is the cause of pneumonia, Friedliinder 

 seems to have considered it extremely probable that it bore an etiological re- 

 lation to this disease. 



During the same year Leyden and Gunther announced at a meeting of 

 the Medical Society of Berlin (November 20th, 1882) that they had found the 

 same micrococcus in the fibrinous exudate of pneumonia, obtained through 

 the thoracic walls by means of a Pravaz syringe. At the same time G-unther 

 stated that the elliptical cocci, in specimens stained with gentian violet, were 

 surrounded with a colorless capsule. 



The following year Matruy published his observations. In sixteen cases 

 he had found an elongated coccus in the fibrinous exudate of pneumonia, and 

 always having a very transparent capsule. He had also encountered the 

 same microorganism in the sputa of patients with other diseases, but not so 

 abundantly as in pneumonia. 



On November 19th, 1883, Friedlander communicated to the Medical Soci- 

 ety of Berlin the results of his culture and inoculation experiments. His 

 " pneumococcus " was characterized by the presence of a capsule which, as 

 he says, " always takes the form of the microorganism; if this is round the 

 capsule is round ; if it is elliptical the capsule is an ellipse." This capsule, 

 however, was only found in preparations made from the blood of an inocu- 

 lated animal or from the fibrinous exudate into the alveoli ; in cultures it 

 was no longer seen. The cultures in flesh-peptone gelatin presented a nail- 

 shaped growth which was believed to be characteristic. Growth was rapid 

 in a variety of culture media at the ordinary room temperature (65 to 

 75 F.), and in a gelatin culture medium no liquefaction occurred. 



The following results were obtained by Friedlander in his inoculation ex- 

 periments: In one series of experiments the " pneumococci," mixed with 

 distilled water, were injected through the thoracic walls into the lungs. 

 Nine rabbits inoculated in this way gave an entirely negative result. Six 



'I should have said frequent instead of " constant presence." 



