368 PATHOGENIC MICROORGANISMS 



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. 



identified as Streptococcus pyogenes, described such capsule formation occurring in 

 the peritoneal exudate of infected rabbits. 



Schuetz' (<Sc/iMei3,Cent. f. Bakt.,Ref. 1, 1887, p. 393) DiplokokkusderBrustseuche 

 der Pferde, Poels and Nolen's (Poels und Nolen, Fort. d. Med., iv, 1886, p. 217) 

 streptococcus of contagious pneumonia of cattle, and especially the organism de- 

 scribed by Bonome {Bonome, Ziegler's Beit., viii, 1890, p. 377) as Streptococcus 

 der meningitis cerebrospinalis epidemica, may all be looked upon as organisms 

 differentiated on insecure grounds from either pneumococcus or streptococcus. The 

 first two of these organisms, however, are said to be decolorized by Gram's method, 

 and as suggested by Frosch and Kolle {Frosch und Kolle, Flugge's " Mikro- 

 organis.,'' ii, 1896, p. 161), in the case of Schuetz' organism may belong to a group 

 intermediate between Fraenkel's diplococcus and the chicken-cholera group. 



Tavel and Krumbein {Tavel und Krumbein, Cent. f. Bakt., xviii, 1895, p. 547) 

 describe a streptococcus with a capsule, which was isolated from a small abscess on 

 the finger of a child. Capsules were also present in the artificial cultures, and 

 although ordinarily remaining uncolored, could be stained by Loeffler's flagella stain. 

 This organism was said to be differentiated from Fraenkel's diplococcus and also in 

 general from streptococcus (pyogenes) by a rapid and rich growth on gelatin, agar, 

 and potato. A pellicle was formed on broth. The organisms forming this pellicle 

 possessed capsules, but those in the deeper portions of the broth generally lacked 

 the capsule. 



In 1897, Binaghi (Binaghi, Cent. f. Bakt., xxii, 1897, p. 273) described a 

 capsulated streptococcus isolated from a guinea-pig dead of a spontaneous peribron- 

 chitis and multiple pulmonary abscesses. In the pus were found some diplococci and 

 short chains (four to six) surrounded by a capsule, which could be made evident by 

 staining with carbol fuchsin. This organism he proposes to call Streptococcus 

 capsulatus. 



Le Roy des Barres and Weinberg in 1899 {Le Roy des Barres et Weinberg, Arch, 

 d. m^d. exp^r., xi, 1899, p. 399) published an account of a streptococcus with a 

 capsule. This was isolated from a, man who had apparently been infected from a 

 horse which had died of an acute intestinal disorder. The patient neglected the 

 infection and died. Diplococci and short chains furnished with a capsule were 

 found in the subcutaneous tissue at the area of infection. The blood, liver, and 



