702 DISEASES OF THE SKIN. 



In the first edition of this work it was stated that " this 

 entozoon is not known to cause disease." Shortly after the 

 book was issued, I was told that this acarus not only caused 

 disease in dogs, but the disease was considered by Continental 

 veterinarians to be incurable; and thanks to Mr. Fleming 

 (see Veterinary Sanitary Science and Police, vol. ii. p. 454), 

 and Mr. W. Hunting (see Veterinary Journal, September 1875, 

 p. 167), the English reading veterinary surgeons were made 

 acquainted with the symptoms and nature of this form of mange. 



The demodox folliculorum found in the dog is identical with 

 that in the human beinsj, in whom it seems to cause no disease 

 or inconvenience. Indeed, according to Erasmus Wilson, the 

 difficulty seems not to be to find these creatures, but to find any 

 individual, with the exception of newly-born children, in whom 

 they do not exist. Gruby transferred the parasite from man to 

 the dog, in whose skin it both hved and propagated. This dog 

 was kept and watched for two years, and in that time all the 

 hair follicles had been invaded, and the hair had disappeared. 

 Mr. Fleming thinks that there may not be a specific identity 

 between that found in man and that of the dog, and further 

 experiments would be interesting ; but the result of the experi- 

 ment of Gruby is very strong evidence of their identity. 



This parasite measures from -g^ to ^Jt of an moh. in length, 

 and from -5V to -g^ of an inch in breadth, and is composed of 

 a head, thorax, abdomen, and a long obtusely pointed tail. 



The head represents in form a truncated cone, flattened from 

 above downwards, and is furnished with two maxillary palpi, 

 which admit of extensive motion. The thorax is the broadest 

 part of the animal, and is composed of four segments, and having 

 four legs on each side. The abdomen varies in length and 

 admits of certain movements; internally an alimentary canal, 

 and a brownich mass, supposed to be the liver. It has a 

 mouth, directed obliquely downwards from the head, and an anus 

 at the opposite extremity of the body. 



The parasites inhabit the sebaceous and hair follicles. Their 

 heads are directed inwards towards the base of the folUcles ; and 

 when very numerous, they are placed back to back, and their 

 feet applied to the walls of the ducts. 



The symptoms and treatment are so well given by Mr. Hunt- 

 ing, that I feel I can do no better than quote them. 



