16 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 
“The destruction of the parasite is effected with great difficulty, arising 
chiefly from the cireumstance of its being enabled so easily to make its way 
to the extreme ends of the hair-follicles and sebaceous glands. Success in 
destroying the Acari depends very much more on the manner in which 
medicinal agents are used than on the agents themselves. The most potent 
destroyers of their life may prove perfectly inert unless properly applied. 
Nothing short of a thorough rubbing in of whatever be used will suffice ; and 
not only so, but it is necessary for the agent to be applied again and again. 
An ointment made with half a pound of lard, two ounces of tar, and four 
ounces of sulphur should be well rubbed in before the fire or in the sun, to 
assist its penetration into the follicles of the skin. The unguent should also 
be allowed to remain on the skin for two or three days, and more friction 
applied daily. When washed off, some carbonate of potash should be used 
with soap and water, so as to thoroughly cleanse the animal. The skin should 
then be dried, and recourse had again to the unguent, This treatment must 
be repeated for at least three or four times. 
“Beyond topical applications none are absolutely required, as success depends 
exclusively upon the destruction of the Acari and their ova. It should, how- 
ever, be borne in mind that many of the parasites may survive, and yet no 
evidence of their existence be observed perhaps for several weeks. For this 
reason the treatment should be repeated at certain short intervals, even in those 
cases where the dog appears to have recovered.” * 
The specimens from different kinds of mammals differ but littlo in 
their appearance from each other, although Leydig considers them to 
be distinct species, In favor of this view the bulk of the evidence goes 
to show that they will not thrive when transferred to a host of a dif- 
ferent kind. 
The form we have had before us closely resembles that from the dog, 
but its body is shorter and wider. One would be rash to consider this 
a constant character, as it may be due to contraction after death. 
CAMBRIDGE, April, 1878. 
* “Observations on Parasites and Parasitic Diseases as affecting Domesticated Ani- 
mals.” By James Beart Simonds. Journ. Royal Agricultural Soc. of England, 2d series, 
Vol. I. Pt. I. p. 72, 1865, 
