NOT DESCRIBED IN PREVIOUS SECTIONS. 



457 



these colonies are a little larger and less transparent; they remain distinct, 

 especially along 1 the margins of the line of growth. Upon potato a very 

 thin, transparent layer is developed, which does not change the appearance 

 of the surface of the potato, but slightly increases its resistance to the plati- 

 num needle. In bouillon small flocculi. suspended in the clear liquid, are 

 developed within twenty-four hours ; these subsequently sink to the bottom. 



Milk is not coagulated by this bacillus, and no gas is produced in media 

 containing- sugar. 



Pathogenesis. Pathogenic for rabbits, guinea-pigs, young rats, and mice, 

 in which animals it produces general infection, and death- in rabbits at 

 the end of twenty-four hours. The bacillus is found in tne blood in great 

 numbers. 



97. PROTEUS VULGARIS. 



Obtained by Hauser (1885) from putrefying animal substances, 

 and since shown to be one of the most common and widely distrib- 

 uted putrefactive bacteria. This and the other species of Proteus 



Fia. 156. Proteus vulgaris; " swarming islands " from a gelatin culture, x 285. (Kauser.y 



described by the same bacteriologist (Proteus mirabilis, Proteus Zen- 

 keri) have no doubt frequently been encountered by previous observ- 

 ers, and are among the species formerly included under the name 

 " Bacterium termo," which was applied to any minute motile bacilli 

 found in putrefying infusions. 



Morphology. Bacilli with rounded ends, about 0.6 /u broad, and 

 varying greatly in length, being sometimes short oval, and at others 

 from 1.25 to 3.75 /* in length ; also grow out into flexible filaments, 

 which may be more or less wavy or spiral in form. The short rods 

 are commonly seen in pairs ; they have terminal flagella ; involution 

 forms are frequently seen, the most common being spherical bodies 

 about 1.6 /u in diameter. In old cultures in bouillon, or in cultures 

 made in meat infusion in the incubating oven, the short oval forms 

 greatly predominate, but in recent cultures in nutrient gelatin fila- 



