BACILLUS PNEUMONLE. 25 



The sheath has exactly the form of the bacillus which it 

 surrounds, and hence it usually presents the appearance 

 of an elongated ovoid ; two to four bacilli in chains are 

 often present in one capsule ; in other cases the division 

 is complete, and each of the new bacilli has its own 

 capsule. The breadth of the sheath is at least as great 

 as the transverse diameter of the bacilli ; at times, how- 

 ever, it is two to three times greater. This capsule 

 formation is not at all peculiar to the pneumonia bacilli, 

 in which, however, the enveloping substance which is 

 present in a very large number of bacteria is particularly 

 well formed ; this material is also quite as great in some 

 other species. 



Cultivations of Friedliiuder's bacilli are readily obtained Cultivations, 

 on very various nutrient substrata. On gelatine plates 

 white points appear after twenty-four hours, and under 

 the microscope present the form of round, sharply- 

 defined discs, with a dark granular centre, and a narrow 

 olive-coloured border ; at a later period a white por- 

 cellaneous deposit is formed on the surface of the 

 gelatine, like a very prominent convex knob. In cultiva- 

 tions made by plunging the needle into the gelatine, a 

 thick, white, confluent mass is formed along the track 

 of the needle, and this mass extends into any fissures 

 which may communicate with this track ; here, also, we 

 iind a convex knob on the surface. In stroke cultivations 

 & thick, white, creamy layer is formed. The bacillus 

 also grows well on agar, blood serum, and potatoes. On 

 the latter whitish-yellow gelatinous masses are formed,- 

 which may extend over the whole surface of the potato, 

 presenting a glistening surface and showing at times a 

 development of gas and formation of bubbles. The rod 

 shape of the bacilli is particularly evident in micro- 

 scopical preparations of cultures, especially when the 

 growth has occurred at a low temperature and the 

 individual organisms have attained their full size before 

 dividing. The formation of spores has not as yet been 

 observed with certainty. 



Friedliinder and Frobenius have performed inocula- r 



, . . , . . . Inoculation on 



tion experiments on animals with pure cultivations of the animals. 



17 



