AND OTHER FERMENTATIVE CHANGES 299 
but had the oval and vacuoled character of the scum of the earlier period, so 
that the specific identity of the two growths was no longer doubtful. 
I afterwards obtained still more satisfactory evidence on the same point. 
The long sprouts observed in the scum of the second glass of urine, a few hours 
after inoculation, seemed to indicate that the very liquid which, when altered 
by fermentation, induced the change of the organism to the toruloid condition, 
favoured, when perfectly fresh, a return to the filamentous form. I therefore 
resolved to watch, if possible, the earliest growth of the spherical cells of the 
scum in uncontaminated urine. For this purpose I proceeded on the same 
principle as before ; but experience having shown that the thin layer of atmo- 
sphere between the glass plates was 
exhausted within a few hours, I tried 
a new arrangement for providing a 
larger supply of air, that which I ulti- 
mately arrived at being as follows :— 
A piece of plate-glass about three- 
eighths of an inch thick, and about 23 
inches by 14 in the other dimensions 
(shown in diagram in the accom- 
panying woodcuts, the lower of which 
represents it in section), is excavated 
by the lapidary into a circular ditch, 
D, round a central island, I, the island 
being three-eighths of an inch in diameter, and the ditch or air-chamber of about the 
same breadth, and as deep as the thickness of the glass will conveniently permit, 
viz. about a quarter of an inch. A piece of thin covering glass, P, sufficiently 
large to cover the ditch as well as the island, but not quite so broad as the glass 
plate, so that it can be conveniently sealed down with paraffin, completes the 
‘glass garden’, which is stocked as follows :—The glasses must first be heated 
and allowed to cool, without access of dust to the air-chamber. The glass plate 
with the cover im situ, and covered further with a larger slip of ordinary glass, 
is placed upon a broad plate of metal on a retort stand, and over this a metal 
lid, such as that of a tin biscuit-box. Heat is then applied to the metallic plate 
by means of a Bunsen’s burner or large spirit-lamp, till a drop of water sprinkled 
on the tin lid above passes off at once by ebullition. The lamp is then removed, 
and cooling is allowed to take place completely. The object of the metal plate 
and lid is to diffuse the heat, and thus prevent cracking of the thick and irregu- 
larly shaped plate of glass. The lid above aids in keeping out dust during 
cooling, and this is further effected by the thin covering glass and the overlapping 
