DIPLOCOCCUS PNEUMONLE 369 



There are occasions, then, both within the animal body and in arti- 

 ficial cultivations, when it is practically impossible to distinguish defi- 

 nitely between some races of pneumococci and races of streptococci. 

 This difficulty is especially heightened when the pneumococcus has 

 become non-virulent, and at the same time no very typical morphology 

 or capsule formation is to be determined and a tendency to chain-forma- 

 tion is marked. Cultures of pneumococci in such condition can not 

 readily be distinguished morphologically from streptococcus cultures. 



Under these circumstances recourse must be had to a careful bio- 

 logical study of the organism in question. The following are the criteria 

 mainly relied upon at present for the differentiation of these two groups. 



Pneumococci ferment inulin, if cultivated in inulin-serum-water me- 

 dium. Acid formation from the inulin results within two days or more 

 in coagulation of the serum and reddening of the litmus. Streptococci be- 

 cause of their inability to attack the inulin leave the medium unchanged. 1 



broth inoculated from the peritoneal exudate of a rabbit dying from the infection 

 gave streptococci in extremely long chains and surrounded by capsules. These were 

 not so distinct as in the case of the organisms in the original smear preparations. 

 All fluid media (bouillon, milk, and ascitic broth) were said to be strongly acid after 

 twenty-four hours. These authors report that Achard and Marmorek have assured 

 them that they have seen capsulated streptococci, and that Marmorek showed them 

 some preparations in which one of his streptococci presented the same characters as 

 that isolated by them. 



Although Le Roy des Barres and Weinberg have used the term encapsulated, 

 they believe that it would perhaps be more prudent to call their organism strepto- 

 coque aureole, since they were not able to define this capsule by staining it. 



Howard and Perkins (Howard and Perkins, Jour. Med. Res., 1901, iv, p. 163) 

 have lately described an organism, probably of the foregoing type, which was present 

 in a tubo-ovarian abscess and in the peritoneal exudate, the blood, and some of the 

 organs of a woman dying in the Lakeside Hospital, Cleveland, Ohio. The organisms 

 were biscuit-shaped cocci in pairs, usually arranged in chains of four, six, eight, 

 or twenty elements, and surrounded by a wide and sharply staining capsule. In the 

 artificial cultures special capsule stains, it was noted, failed to stain any definite area, 

 but numerous small deeply stained granules were to be seen within the halo, espe- 

 cially near its outer border. Howard and Perkins propose for the group composed of 

 the streptococci of Bonome, Binaghi, and their own organism, the name Strepto- 

 coccus mucosus. Streptococci isolated from cases of epidemic sore-throat have also 

 shown capsules (p. 343). 



Reference to the original descriptions of these various capsulated streptococci 

 will show that, with the exception of a rather poorly staining capsule, the majority of 

 these organisms are separated from the typical Streptococcus pyogenes or from the 

 pneumococcus by exceedingly slight and unstable morphological and cultural char- 

 acters. This is true of the difference in their pathogenic action in animals. 



1 Hiss, Cent. f. Bakt., xxxi, 1902; Jour. Exp. Med., vi, 1905. 



