Abstract
The itch mite, Psoroptes communis var. cuniculi, is a common ectoparasite upon the rabbit, large numbers being found upon the skin surface deep within the fold of the outer ear. The skin where the mites occur becomes necrotic and is sloughed off. If a small piece of the slough be examined with a low-power microscope, many mites can be seen crawling over it.
It has occurred to the writer that repeated skin puncture by such numbers of ectoparasites, each injecting in the form of its saliva a small quantity of protein peculiar to the parasite, should lead to the production of specific antibody against the attacking species. We have endeavored to determine if this be true by testing for the presence of precipitin in 10 adult rabbits, 5 known to be infested with the parasites, these being observed in each case under the microscope, and 5 others apparently free of such infestation, neither the parasites nor their characteristic effects being detected upon careful search.
The antigen—an extract of the mite—was prepared in the following manner. Pieces of the sloughed skin were removed with forceps from the infested ears and placed in a Petri dish. As we observed them with a low-power dissecting binocular, the mites could be seen to leave the skin and crawl about over the glass plate. They were picked up, best in groups of several, on the point of a dissecting needle and transferred to a small mortar. After about 300 mites were thus transferred, they were mashed with a pestle and triturated for 10 minutes with 1 1/2 cc. of Coca's solution. The mixture was then centrifugated at high speed and the very slightly opalescent supernatant fluid decanted.
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