22 
Hogg, on Vegetable Parasites. 
From these experiments I believe that it matters little 
whether' we take yeast, achorion, or penicillium spores, the 
resultant is the same, and depends much more on the food 
or nourishment supplied whether the pabulum contains more 
or less of a saccharine, albuminous, or nitrogenous material, 
lactic acid, &c., together with light and temperature ; whether 
we have a mould (green or blue), an achorion or yeast fun- 
gus produced. Diversity of form in the cells, as well as 
quality and quantity of their material contents, is certainly 
due to, and in a manner regulated and controlled by, the beau- 
tiful law of diffusion, which admits, separates, sifts, and 
refines the coarser from the finer, the lighter from the denser 
particles, through the porous structure of the cell-wall. 
In conclusion, I trust I have satisfactorily shown that — 
1st. There exists but one essential organism, a fungus 
whose spores find a soil common alike to the surface and the 
more secluded parts of the human or animal body. 
2nd. That variations in skin diseases associated with para- 
sitic growth are due to diflPerences in the constitution of the 
person affected ; to the moisture, exudation, soil, and tem- 
perature, under which the development of the fungus takes 
place. Consequently it is neither correct nor desirable to 
separate and classify them as "parasitic diseases of the skin/' 
3rd. The parasitic growths vary but little in any case, and 
that only in degree, not in kind, some soils appearing to be 
better suited than others for their development, that fur- 
nished by the eruptive or secreting surface being in every 
way the most congenial ; while diversity of form, in all cases, 
arise from growth taking place either upon a sickly plant, 
a saccharine solution, or an animal tissue. 
Should there be fatty matter mixed up with the specimen, it will be neces- 
sary to remove the cover and add a drop of ether ; then wash it with dis- 
tilled water. Other reagents will, from time to time, be found requisite, 
and enable us to avoid errors in interpretation ; as, for instance, on the 
addition of a drop of hydrochloric or acetic acid all earthy particles are 
dissolved out. Ether, chloroform, or alcohol, readily remove fatty matters. 
A solution of potash or soda will dissolve out pus, epithelium, &c., and more 
quickly so if the specimen be slightly heated, while fungus-spores are not 
affected thereby, but, on the contrary, are better seen. In some chronic 
cases of skiii disease we find the epithelium-scales involved in a kind of 
/aitj/ degeneration, minute fat-globules, which at first sight bear a vety strong 
resemblance to spores ; these must be got rid of by soaking in ether, and 
then washing with strong liquor potassse. Like other vegetable cells, spores 
sometimes require the addition of a drop of iodine, which renders them dis- 
tinctly visible. View all specimens, first, with monochromat light, and after- 
wards with polarized light. The latter shows up the starch-granules, if 
present, and distinguishes the granular particles of earthy matters. Por 
mounting and preserving the specimen, use glycerine jelly, or glycerine 
diluted with one third of camphor water. 
