1893.] An Extreme Case of Parasitism. 351 
tioned. Itch mites were found in abundance, and the nature 
of the disease was soon established. 
In order to study the case more thoroughly, a number of the 
scales were prepared by usual histological method. The scales 
were fixed and hardened by immersion in alcohol, stained in 
picrocarmine, finally imbedded in paraffin, sectioned, affixed to 
slides with clove-oil collodion, and mounted in series. The 
shrinkage in passing through this process was very slight. The 
differential staining in this case was peculiar: the epithelium 
stained red, the mites yellow; the eggs remained unstained, 
that is, white; the fæces appeared dark brown or black. In 
staining sections of normal skin with picrocarmine, the outer 
or horny layer stains a bright yellow, the underlying proto- 
plasmic layers stain more or less deeply red. In the present 
case the epithelium is peculiar in that well-stained sections 
show very little yellow; this indicates that the component 
cells are still protoplasmic, and have not cornified. 
The activity going on in the columnar layer to replace this 
constant and enormous loss of cells must have been great. 
Apparently a vicious circle was established; the presence of 
the mites irritating the skin—the skin, to protect or rid itself 
from the parasites, pushed out a large number of new cells. 
These succulent cells, however, furnished a good nidus for the 
mites. The mites increased, causing increased irritation of the 
skin, and this caused an increased proliferation of cells. Thus 
the case went on, until it assumed this extreme form. 
I may here say, that under appropriate anti-parasitic treat- 
ment at the hospital, the mites were soon exterminated. The 
cause of the irritation once removed, the skin gradually 
regained its normal character. 
NUMBER or Mires.—In®*order to obtain an idea of the num- 
ber of mites present on the host, that is, at the time the mites 
were present in greatest numbers, several scales were cut to 
measure one-half by one-eighth inch, sectioned and mounted 
serially. It will be readily understood that in such a pro- 
cedure the mites were cut in various planes and directions; 
sometimes the head would be seen in one section, the body in 
one or two other sections, and the tail in still another. Many 
of the smaller embryos and eggs appeared entire. 
