PRODUCERS OF ABSCESSES, CELLULITIS AND SEPTICAEMIA 337 



and kidneys. Intraperitoneal injections given to guinea-pigs and mice 

 are followed by purulent peritonitis, beautifully formed cocci in groups 

 of four being obtained in immense numbers from the exudate. Rabbits 

 and dogs are not affected by large doses of a culture subcutaneously or 

 intravenously administered. 



The serum from immunized cases has not been used therapeutically 

 in human infection. 



THE STREPTOCOCCI. 



Under this name must be included not only the streptococci which 

 excite inflammation in man, but all spherical bacteria which divide, as 

 a rule, in one plane only and hold cocci together in greater or lesser 

 chains. This name comprises by no means so many varieties of bac- 

 teria as are grouped under the title bacilli. There are, nevertheless, a 

 considerable number of distinct groups of streptococci which differ 

 decidedly both in their cultural characteristics and their pathogenic 

 properties. The streptococci average about 1 in diameter. None 

 of them form spores or are motile. They are rather easily killed by 

 disinfectants. Those that are pathogenic develop wholly or almost 

 so in or on the bodies of man and animals. 



Streptococcus Pyogenes. The group of streptococci which in its 

 importance as related to human infections outweighs all other strepto- 

 cocci, is that which comprises the streptococci which excite erysipelas, 

 many cases of cellulitis, abscess, septicaemia, pneumonia, etc., and 

 passes under the name of streptococcus pyogenes. 



This organism was first discovered by Koch in stained sections 

 of tissue, attacked by septic processes, and by Ogston in the pus of 

 acute abscesses (1882). It was obtained by Fehleisen (1883) in pure 

 cultures from a case of erysipelas, its cultural and pathological charac- 

 ters studied and demonstrated by him to be capable of producing 

 erysipelas in man. Rosenbach (1884) and Krause and Passet (1885) 

 isolated the streptococcus from the pus of acute abscesses and gave it 

 the name of streptococcus pyogenes. It has since been proved to be 

 one of the chief etiological factors in the production of many suppu- 

 rative inflammations. Formerly the streptococci of erysipelas, acute 

 abscesses, septicaemia, puerperal fever, etc., were thought to belong 

 to different species, because they were observed to possess apparent 

 differences in their biological and pathological characteristics, accord- 

 ing to the source from which they were obtained. Thus one species of 

 streptococcus was believed to be capable of causing erysipelas only, 

 another only acute abscesses, another sepsis, etc., but it is now known 

 that the slight differences between the majority of these streptococci 

 are but acquired variations of organisms derived from the same species 

 which are not permanent. 



Morphology. The cocci, when fully developed are spherical or oval. 

 They have no flagella or spores. They vary from 0.4// to l/i in diameter. 

 They van- in dimensions in different cultures and even in different 



22 



