1895.] The Etiology of Small-Pox. 705 
no staining revealed any living organisms. Some of the round 
bodies observed in ten different examinations may have been 
spores or micrococci, but their nature was not revealed by the 
microscope. 
A series of plate cultures upon “ Pasteur gelatine ”® was then 
arranged, but there occurred no development. These plates 
were prepared from 10 parts of gelatine to 90 parts of Pasteur’s 
fluid. So, test-tube cultures in Pasteur’s fluid alone, and in 
bouillon (beef; one pound of meat to one liter of water) ren- 
dered alkaline by Cl Na. were made. The points were grasped 
with a forceps, passed through a flame, and dropped into the 
medium which had been, previously, submitted to a very 
thorough fractional sterilization, as by the usual preparation 
of medium supplies. Great care was exerted in order that 
no infection from without should take place. 
By a temperature of 24°C. the culture fluid would, on the 
next day after inoculation, become slightly turbid; on the 
second day the turbidity increased, a thin film being formed on 
the surface, and on the third day a grayish, highly tenacious 
film made its appearance. Microscopic investigation showed 
the presence of bacilli. The latter are colorless; they exhibit 
no motion, are devoid of cilia; their long diameter measures 
0.6-1.0 » and the short diameter .2-.34. During the first and 
second days, they seem to develop in colonies of 20-200 cells, 
although, under the cover, many cells appear to be free and 
isolated. 
The zooglea (surface-film) has, to a great extent, the same 
appearance as the film-growth of the yeast-like Mycoderma, 
being folded, and of a greasy appearance. It is so tenacious 
that it resists the weight of the column of the culture medium 
which was observed as one of the cultures chanced to be 
inverted. Its connection with the culture vessel is quite 
intimate. On the fourth days, fragments of the zooglea began 
to descend to the bottom, and the macroscopic appearance of 
the culture remained, after this, unaltered for three weeks and 
more. During this period, however, the microscopic appear- 
ance of the bacillus was gradually much modified. 
38 See Salomonsen, Bacteriological Technology, pp. 460 and 464. 
