144 
ANNALS OF THE 
in a state of immaturity. So singular is this power of being so retained, that we 
might almost reduce it to a formula. Giving a certain quantity of sustenance we 
might predicate the form which the parasite would exhibit, and thus we find no 
difficulty in accounting for the great variety which is met with on the human sub- 
ject alone ; difference in density and chemical constitution of textures, in degrees 
of warmth and moisture, in greater or less facility of access to external air, will 
readily account for these differences in form, and will render it no matter for sur- 
prise that microscopists should have given distinct specific names to upwards of 
thirty plants which are in truth referable to one or two. 
There remains one very peculiar variety to be mentioned. This consists of 
minute square-shaped cells arranged in fours. It was discovered by Professor 
Goodsir, in a disease of the stomach, and was named by him Sarcina ventricuU. A 
similar one has been observed by Dr. Gardner and others, from the kidney. There 
is now good reason to believe that both these are merely varieties of the common 
fungi of which we have been speaking, Penicillium and Aspergillus, for identical 
growths have been found by Mr. Stephens, on bones from South America ; by Dr. 
Fox on the human subject, in a case of skin disease ; and by myself in a phial con- 
taining crystals of cholesterine. 
Let us now enquire into the power which fungi have of generating disease. 
Their influence upon plants has never been doubted — Firstly, because their ravages 
are too well known, and too serious, to admit of dispute ; and secondly, because 
their malific agency upon structures of a low organization, allows of more easy de- 
monstration, than when highly organized and sensitive tissues are the seat of their 
operation, and when more various forces and conditions are to be considered- 
It is no difficult matter to show that dry-rot as it is termed, would be a com- 
paratively slow process, were it not that the fungus is present, to insinuate itself 
amongst the fibres of the wood, to give admission to air, and to yield oxygen, which 
hastens the already commenced decomposition ; while at the same time the living 
cells abstract chemical elements from the woody fibre, and fan into activity the ere- 
macausis or slow combustion of the decaying tissue. Equally obvious is the fact 
that without yeast, wort would undergo but little fermentation, and that if all vege- 
table organisms were excluded, no proper fermentation w^ould result ; for even in 
the case of wine which is conducted without the artificial aid of yeast, I have found 
that this is really the source of the fermentation. 
We may assume then, as a fact, which few will deny, that a living vegetable 
parasite upon other vegetable cells, must excite in them a chemical action, equiva- 
lent to fermentation, for it cannot grow without so doing ; and that even supposing 
the cells themselves were able to resist this action, the juices of the plant, not pos- 
sessed of the same vital resistance, must succumb to its influence Whether this 
alone be the real secret of its power, affects not the question. If the juices are de- 
