440 
ON THE ACARUS. 
I have only seen the acari of mangy dogs, and they greatly 
resemble the horse acari, but are smaller, and have far thicker 
hairs on their sides, which almost look like feathers. 
It is very probable that, under favourable circumstances, the 
acari from dogs and cats will pass on to human beings, and other 
animals; but though Gohier found, by his experiments, that 
they really bored through the skin of other animals, yet many ob¬ 
servations serve to shew that the acari of dogs and cats, like 
those of cattle, die without producing any disease, when placed 
on the skin of man or any other animal. 
B. Amoreux states* that sheep, cows, and dromedaries were 
infected by a mangy dog that was kept with them. 
Grognierf gives an account of a young man who had handled 
a mangy dog, on whose hands and arms an eruption appeared 
very similar to the mange. VilborgJ says, a gentleman and his 
wife, who had been in the habit of fondling a mangy pug dog, 
were almost covered by an eruption very much resembling 
the mange in dogs. I myself have seen two boys who were in¬ 
fected by a mangy poodle, and a girl by a mangy cat; and I also 
once saw the disease communicated to a horse by a cat which 
had lain on his back while he stood in the stall. 
Walz discovered acari on mangy foxes, which were only half 
so large as those of the sheep, and which, when taken from the 
fox, could scarcely be kept alive for a single day, although the 
same means were made use of as those by which the sheep acari 
were kept alive for several weeks. Walz does not describe their 
form. He states, that these acari were placed on two healthy 
sheep, and produced no visible effects; whence he concludes, 
that the opinion which is so prevalent in many countries, that 
sheep are infected by mangy foxes, is without foundation. I 
think that here, as in other similar cases, one or two experiments 
ought not to be considered as decisive. 
I have often seen dogs become mangy when they have been 
biting mangy foxes, or when they have gone into their burrows; 
and many sporting men believe that the mange will pass from a 
fox to a horse, as the latter have become infected from a dead 
fox being placed on their back after the chace was over. 
Since, then, it is clearly proved by the foregoing statements 
that insects are found in the itch of the human being and the 
mange of animals, which so closely resemble each other that 
they must be considered in natural history as only varieties 
* Lettre sur la M^decine Veterinaire, tom. i., p. 20. 
t Bericht iiber die Tliierarnzeischule zu Lyon. 
I Velerinar-Selskal). Skrifter, decl ii, s. 194. 
