718 
THE PRINCIPLES OF BOTANY. 
yeast plant is found in all fermenting fluids, and, indeed, the 
process called fermentation is due to their presence. 
The practical object of fermentation in the preparation of 
the different drinking fluids which we enjoy is the conversion 
of sugar into alcohol, and by a further extension of the pro¬ 
cess into acetic acid; both of these in their state of dilution 
in wine, beer, cider, &c., are extremely wholesome in their 
moderate use. So even spirits, which consist of alcohol and 
flavouring materials of various kinds, must be admitted to act 
as stimulants upon the animal economy, and to be of the 
highest use and importance. These, then, afford some of the 
good resulting from the effects of the growth of the yeast 
plant. Nay more, yeast itself has been employed as a remedial 
agent, both externally as a cleanser of wounds, and internally 
as a peculiar kind of alterative and stimulant. 
But although its power is beginning to be acknowledged, 
when properly exhibited under the control of the practi¬ 
tioner, yet this should lead us to expect that it might exert a 
baleful influence when present where it is not required, and 
it is therefore of importance that the medical man should be 
able to recognise it. In order to do this we give the annexed 
wood-cut and description of this lowest form of plant from 
Demonstrations of Microscopic Anatomy, by Dr. Harley and 
Professor Brown:— 
Torula cerevesice. (Fig. 218, p. 259.) 
This plant is found in fermenting fluids, in yeast, and in 
saccharine urine. It occurs also in the mouth, oesophagus, and 
stomach. 
“ It consists of numerous round or oval cells, containing in 
their interior minute granules resembling excessively minute 
oil globules. 
“ The mode of propagation is by a species of budding; each 
cell gives forth one or two minute projections, which become 
