AND iS BEARINGS ON PATHOLOGY 385 
refracting character, but attains dimensions about equal to the transverse 
diameter of the thread in which it grows. 
Nor have we any right to assume that because some kinds of bacteria have 
germs, the same must necessarily be the case with all. A priovz there would 
seem to be no organisms known to us in nature with less necessity for such 
a provision. They constitute, in fact, in the adult form,a reproductive apparatus; 
perpetually multiplying with amazing rapidity by fissiparous generation. And 
further, it seems very likely that bacteria, differing widely as they do in their 
characters, may spring from various sources. I have, on several occasions, seen 
appearances which make me think that some bacteria take their origin as seg- 
ments of the threads of minute filamentous fungi. Certain it is that some such 
free segments or gemmae, as they are termed by the fungologist, have morpho- 
logical characters absolutely undistinguishable from some bacteria.’ And, 
supposing any bacteria to have such an origin, we may be pretty sure they 
would not possess germs, seeing that gemmae are themselves a form of germ 
of the fungi that produce them. In the same way there are ciliated monads 
which a few years ago would have been unhesitatingly regarded as definite 
species, but which are now well known to be the spores of various algae and 
fungi; while there are others which have been proved to be adult organisms 
with special reproductive arrangements.” 
The method of investigation which has been described in this communica- 
tion affords the opportunity of judging regarding any kind of bacterium con- 
tained in a particular liquid, whether in reality germs are present as well as 
the adult form. For if we find that the number of fermentative particles corre- 
sponds exactly with the number of adult bacteria which we have counted, we 
may infer that there were no free germs present in the liquid. Thus we may 
fairly suppose that the Bacteriwm lactis exists in souring milk only in the bacteric 
form in which we see it, although it is, of course, possible that it may form germs 
under other circumstances. Meanwhile the facts which I have adduced will, 
I hope, remove the mystery attendant on the notion that water teems with 
ultra-microscopic or invisible germs of the bacteria which we see of larger or 
smaller dimensions in organic liquids undergoing fermentative changes. 
1 See Trans. of Royal Soc. of Edinb., loc. cit., and Quarterly Journal of Microscopical Science, loc. cit. 
2 See the beautiful researches of Dallinger and Drysdale on the life-history of the Monads, Monthiy 
Microscopical Journal, August 1, and December 1, 1873; January 1, March 1, and December 1, 1874; 
and May 1, 1875. 
LISTER I Gc 
