166 J. COSSAR EWART, 



similar to but easily distinguishable from a group of micro- 

 cocci. 



If a particular group of sporules are next watched they 

 may be seen to germinate (Plate XI, fig. 4 ; Plate XI, fig. 25). 

 Dr. Koch states that the rods are developed from the gela- 

 tinous-looking capsule, and not from the bright shining 

 spore. From what I have seen I think there can be no 

 doubt whatever that the capsule takes no active part during 

 the formation of the rod. The sporule first slightly elon- 

 gates (Plate XI, fig. 4, and Plate XI, fig. 25), and then from 

 one of its poles an opaque process appears, which, as it 

 slowly lengthens, pushes the capsule before it as it would an 

 elastic membrane. The capsule, as this stretching goes on, 

 becomes at last so thin and transparent that it can no longer 

 be distinguished from its contents (Plate XI, fig. 5). 



Contrary to one's expectations the remains of the spore or 

 sporule retaining its original brightness persists a consider- 

 able time after the rod has been fully formed. Whether it 

 disappears altogether I cannot say. I have often seen in 

 rods a small oval body, which might either be looked upon 

 as the remains of the spore, as a nucleus, or as a vacuole 

 (Plate XI, fig. 7). Very interesting results are often obtained 

 when the same cultivation is kept under observation for 

 twelve or fourteen days. By this time probably both the 

 oxygen in the small amount of enclosed air and the 

 nourishment in the drop of aqueous humour has been 

 exhausted, hence not only do we find apparently degene- 

 rative changes taking place in the spores, but the filaments 

 are also modified. In fact, the newly formed rods may 

 scarcely increase at all in length (Plate XI, fig. 26), but 

 even in such rods new spores, as large and as well formed as 

 those of the first generation, may appear. Even when the 

 rods increase from three to ten times in length only a very 

 few spores may be formed, and these at very irregular inter- 

 vals. That these modifications result from want of proper 

 nourishment we may safely infer, seeing that when fresh 

 aqueous humour is added, the formation of filaments and 

 spores goes on again as actively as in a fresh preparation. 



Several experiments were made in order to ascertain 

 whether the presence of other bacteria in any way infiuenced 

 the development of bacillus. 



I. A piece of spleen containing rods was placed on the 

 warm stage. At first the rods began to lengthen out into 

 filaments in the usual way, but when the filaments were 

 with the No. 8 Hartnack apparently two inches in length 

 currents of impure air were admitted under the cover glass 



