182 BERKELEY, ON CRYPTOGAMIC BOTANY. 
their growth is encouraged, and steps are even taken to inoculate untainted 
cheeses; but in other instances they are a destructive poison, unless, indeed, 
the evil effects which have arisen from the use of certain mouldy provisions 
are to be ascribed to the decomposition of the matrix, rather than to the 
mould itself. Some of the species are developed with extreme rapidity, and 
a few years since, when the barrack bread was so much affected at Paris by 
a species of Penicillium, a very few hours were sufficient for its development, 
and the mould was in active growth almost before the bread was cold. 
Indeed, it was proved satisfactorily that the spores of this species are 
capable of enduring a temperature at least equal to that of boiling water, 
without losing their power of germination: Such facts, then, are no proof 
of spontaneous or equivocal generation. Dutrochet found, indeed, that the 
chemical nature of substances had great influence on the species which grow 
upon them, and that albumen was almost a perfective preventive. This, 
however, is simply in accordance with facts relative to the distribution of 
Phenogams over the surface of the earth. The chemical composition of the 
soil has a great deal to do with that distribution. The occurrence of 
moulds in closed eavities has been mentioned above, and the extent to which 
the spores or other reproductive bodies insinuate themselves in the most 
deeply tissues. Dutrochet professes to have seen milk-globules changed 
into the spores of moulds, or at any rate developed into moulds. Certain it 
is, that when milk is arrested for a long time in the udder of the cow, and 
forms clots there, moulds are frequently found, and that they find their way 
into cavities which are almost closed to external influences, as in the urinary 
bladder of man, and that under more than one form. Such anomalies may 
at first surprise us, but they may, nevertheless, admit of explanation, as the 
presence of the larvee of tape-worms in deep-seated organs, and even in the 
brain, which was so long a stumbling-block of science. On surfaces freely 
exposed to the air, as the pulmonary cavity, or communicating with it occa- 
sionally, as the walls of the stomach, they are not unfrequently developed, 
under peculiar conditions of disease. 
“One of the most remarkable qualities possessed by certain moulds is 
the power they have of producing or accelerating fermentation. Yeast is, 
in fact, nothing more than a peculiar condition of a*species of Penicillium, 
which is capable of almost endless propagation, without ever bearing perfect 
fruit. Attempts have been made to show that the structure of yeast- 
globules is different from that of ordinary moulds, but without success. 
It appears that wherever exosmose and endosmose take place, there is 
chemical action; and thus, when yeast is mixed with any saccharine matter, 
a multitude of points are presented at which an active interchange is going 
on between the contents of the globules and the external fluid, and at 
which chemical action can take place. ‘The process is only accelerated by 
the presence of the ferment, or rather the fermentation is regulated, and 
the putrefactive and acetous fermentation which might otherwise be esta- 
blished, effectually controlled. Under proper conditions of temperature, 
the acetic fermentation will take place on the application of yeast, but not 
so surely or speedily as by the mycelium of the Penicillium, which is known 
under the name of the Vinegar plant, a filamentous condition instead of 
vesicular, 
“The production of yeast depends upon the extreme facility with which 
moulds adapt themselves to peculiar circumstances. The proper position of 
such moulds is upon the surface of decaying substances ; but several species 
are capable of sustaining life when completely immerged. In such a con- 
dition they cannot produce any real fruit, but they are propagated by means 
of shoots from the mycelium. Substances, which rani prove fatal to many 
other vegetables, as solutions of arsenic, opium, and many other poisonous 
