PARASITES AFFECTING THE SKIN 3 
2. Microsporon.—-In addition to ordinary spore forma- 
tion within the segments, Microsporon develops lateral 
reproductive branches, which bear conidia. 
3. Achorion.— The mycelium consists of much- 
branched hyphz, which may or may not be segmented, 
and are sometimes straight and sometimes curved, 
They break up into spores when ripe, and hence, when 
examined microscopically, one sees between the branches 
of the mycelium large numbers of triangular, round, or 
oval spores. The variation in shape depends upon their 
degree of development. The whole growth forms a 
crust of a yellowish colour, and is in reality a pure 
culture of the fungus. 
In order to examine these growths microscopically, 
one proceeds by scraping the deeper parts of the crusts 
and soaking the material obtained in diluted liq. 
potassz, in order to dissolve out the fat. The prepara- 
tion is then placed on a warm slide, and stained with 
lactic blue. It is best mounted in glycerin or glycerin 
jelly, and a cover-glass applied. 
Ringworm occurs chiefly in two forms—the Tricho- 
phyton and the Achorion form, which is known as favus, 
or honeycomb, ringworm. There has been much dis- 
cussion as to whether these are distinct parasitic affec- 
tions, or whether they both are variations of a common 
type. In the skin lesions marked differences between 
them are apparent, for while the eruption produced by 
Trichophyton is widely dispersed and rounded in shape, 
that produced by favus is yellow, and occurs in the 
form of large crusts. 
Predisposing Causes.—As in most other parasitic 
diseases, dirty surroundings and a debilitated condition 
of the host afford increased facilities for the growth of 
the fungus. Old animals are less commonly affected. 
Certain sheds on farms where the disease is prevalent 
convey infection to each fresh batch of calves, owing 
