490 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vout. VI. 
date into a greenish-blue compound. The cells, washed with distilled 
water and dehydrated, were mounted in balsam. 
The species studied were Saccharo myces cerevisiea, S.Ludwigiz,and two 
found in cultures obtained from the throat in suspected cases of diph- 
theria. The specimens of S. cerevistee and S. Ludwigzt; employed for 
the purposes of preparation, were in the actively growing condition in 
Pasteur solutions, from which a quantity of the cells, separated by 
centrifugalization, was taken hourly, starting with the commencement of 
growth, up to the twentieth hour, and treated as indicated above. Cul- 
tures of S. Ludwzgiz, in the sap of the iron-wood tree, Ostrya virginica, 
and of the maple, gave very valuable and instructive preparations. For 
the study of sporulation S. cerevzse@ was used, the sporulation having 
been brought about by cultivation in a 5 per cent. solution of sugar, as 
indicated by Wager. | 
III.—GENERAL CELL STRUCTURE. 
In the fresh yeast cell at the beginning of fermentation, even with the 
highest powers of magnification, very little can be made out, except the 
occurrence of granules and vacuoles. ‘These are grouped irregularly in 
the cell and their number and character may vary, although asa rule 
there is but one large vacuole. In some young, actively growing yeast- 
cells, that is in those which are observed two hours after the commence- 
ment of fermentation, there may be no vacuoles observable. In such, 
however, one or more granules may be found. This condition may be 
observed also in cultures of from sixteen to twenty hours. 
Many of these granules appear to possess a fatty nature. When the 
yeast cells of this stage are hardened in Flemming’s fluid for twenty-four 
hours the granules take a dark tinge, due apparently to the reduction of 
the osmic acid derived from the solution. They are not nearly as 
numerous in preparations hardened in alcohol as they appear to be in 
the fresh cell. Ata later stage of fermentation the granules present are 
of a different composition. They do not react, or at most react but 
slightly, with the osmic acid of Flemming’s fluid. They seem to be of a 
purely proteid character, for when the hardened cells are heated with a 
solution of potassic plumbate the granules acquire a light brown colour, 
this fact indicating the presence of organic sulphur. These granules 
were found to react also with freshly made Millon’s reagent in from 
eight to ten hours without the application of heat. 
ee. 
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