MITES OF LOWER ANIMALS. 51 



which resemble the true Sarcoptes Hominis in structure, and 

 only differ from it in size. In this case we must beware of 

 errors which may easily be produced by our not noticing the 

 constant fresh, perhaps daily, infection taking place during the 

 long contact of mangy animals with the same human individual; 

 and supposing, from the long duration of the animal-mange upon 

 the man, thus caused, that the specimens of the mite found have 

 grown large upon the man, whilst they have probably, in gene- 

 ral, only been transferred to him a short time before. What 

 has been said of the possibility of a development of the mites 

 of animals through their particular phases upon the human body, 

 applies especially and perhaps solely to 



1. The true Sarcoptes of the cats, which, however, may also 

 be transferred to dogs, hyaenas, bears, sheep, apes, and Guinea- 

 pigs, as well as to men. It is well known that the true Sarcoptes 

 Catorum, the male of which I figured formerly in Giinsburg's 

 { Zeitschrift/ is only about one half smaller than the Sarcoptes 

 Hominis. I omit to reproduce the figure here. It is only 

 necessary to look at the figure of Sarcoptes Hominis, and 

 imagine the animal smaller and more delicate. The size of 

 the female of this Sarcoptes is only 0*05 O06'" in length, 

 and 0'05'" in breadth, so that the body of the animal appears 

 almost circular. It is only furnished with weak hairs; its feet 

 are delicate, but distinctly jointed in the same way as those of Sar- 

 coptes Hominis ; the four anterior feet in both sexes are furnished 

 with suckers ; in the female the two posterior pairs are each pro- 

 vided with a long bristle, and without a sucker ; in the male the 

 third pair with a hair, and the last with a sucking cup on each 

 foot. Recently Bourguignon has described the transfer of the 

 mite of the lion to man, and vice versa. This mite is said to be 

 larger than the cat-mite, and exactly like that of the human 

 subject. It now becomes a question whether the mites of the 

 cat, lion, and human subject are not perfectly identical, and only 

 attain a different size according to the animal which they inhabit. 



2. Sarcoptes Canis. Even Sauvages (' Nosologia/ Amstelod., 

 1763, ii, p. 464) and Viborg speak of a Scabies canina 

 dog's itch, in the human subject; and Hertwig saw two boys 

 infected by a mangy dog. The dog's mite has a great similarity 

 to the horse-mite, except that the former is smaller and has far 

 stronger hairs, which even appear plumose, on the sides of its 

 body. 



