16 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 



"The destruction of the parasite is effected with great difficulty, arising 

 chiefly from the circumstance 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 poimd 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 iised 

 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 little 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 Avould be rash to consider this 

 a constant character, as it may be due to contraction after death. 



Cambridge, April, 1878. 



* " ObserA-ations on Parasites and Parasitic Diseases as affecting Domesticated Ani- 

 mals." By James Beart Simonds. Joum. Royal Agricultural See. of Eugland, 2d series, 

 Vol. I. Pt. I. p. 72, 1865. 



