THE INFECTIOUS DISEASES. 213 



Characters of the Group. 



The bacilli of this group may be ae"robes or facultative anaerobes. They are of 

 medium size, asporogenous, and while staining readily with ordinary dyes are apt to be 

 decolorized by the Gram method. While the organisms of this group are bacilli, they 

 often present considerable variation in form as they grow, sometimes being very short 

 so as to resemble cocci, sometimes forming threads which may be so bent as to suggest 

 spirals. Their growth on solid media is especially characterized by the tendency to 

 send runners from the central growth out into the surrounding media, thus establishing 

 secondary growth centres. They are particularly sensitive to environment, so that 

 physiological as well as morphological variations are frequent. It is for these reasons 

 that the name Proteus has been given to the group and to various species. The limiu- 

 tions of the named species are, however, in many cases quite ill defined. 



One of the most common forms has been called Proteus vulgaris. 

 While this bacillus is very widespread, it is only occasionally the exci- 

 tant of pathological processes in man, and then almost always in concur- 

 rence with other organisms, usually the pyogenic cocci. Under these 

 conditions a suppurative inflammation with foul exudate is apt to de- 

 velop. Thus it has been found in purulent peritonitis and endometritis, 

 in pleurisy and in phlegniouous inflammation in various parts of the 

 body. Although this bacillus is not apt to grow in the human body, 

 except in association with other micro-organisms which may damage the 

 tissues or in tissues already vulnerable from injury, it may in the blad- 

 der independently incite an exudative inflammation. In animals, sub- 

 cutaneous injection of the pure culture in considerable quantity may 

 lead to abscess, while the soluble products of broth culture may induce 

 toxaemia. 



Several other forms of Proteus, as well as closely related species, 

 have been found in human lesions for the most part suppurative and 

 necrotic in character and these, in some cases, have been conclusively 

 shown to be the excitants of the pathological processes, but the scope of 

 this work does not permit further details. ' 



Among the other bacteria which commonly induce local suppuration, 

 with or without toxaemia and septicaemia, some are of frequent occur- 

 rence as excitants of such well-marked and more or less characteristic 

 forms of disease as have long been recognized clinically and have re- 

 ceived special names, such as pneumonia, gonorrhoaa, cerebrospinal men- 

 ingitis, etc. These will be in part considered in the section dealing with 

 the organs in which their more characteristic lesions are manifested. 



ACUTE LOBAR PNEUMONIA AND OTHER INFECTIOUS DISEASES 

 INDUCED BY THE MICROCOCCUS LANCEOLATUS (Diplococcus 

 Pneumonias). 



Micrococcus lanceolatus is frequently spoken of as the " pneumococcus 

 of Frankel, " because its significance and life history in connection with 



1 These may be found in Kruse's article on "The Bacilli " in Flilgge's "Mikroorga- 

 aismen." last edition. 



