THE GENUS DEMODEX. 9 



market because of a peculiar appearance of the skin which was shown 

 to be caused by Demodex." 



At first only isolated pustules are present, their size varying from 

 that of a grain of sand to that of a hazelnut. They are often very 

 numerous and may be situated close together ; sometimes they become 

 confluent. A very large number of mites are present in the larger 

 pustules. The parasites are only found in places where the skin 

 is fine in texture (see above). Some of the pustules are pigmented 

 and may be situated rather deeply and surrounded by an inflamed area. 

 The disease does not seem to affect the general health of the animal. 



Hollister states that this type of mange usually spreads very slowly, 

 and only a few animals in the herd are aff'ected. It is best to get rid of 

 the infested animals and to disinfect the premises. 



The Demodectic mange of the Goat is characterised by little pustules 

 varying from the size of a pea to that of a walnut. Sometimes they 

 are placed on the surface of the skin but in other cases they are situated 

 deeply and are not visible on the surface. These pustules contain a 

 greyish matter with numerous specimens of Demodex in all stages of 

 development. These more deeply situated nodules are only visible 

 when the skin of the goat is taken off (for they are situated on tlie 

 inner surface) ; when the skin is being tanned holes appear at the 

 places where the nodules occur and greatly lessen its value. According 

 to Ilissling (as reported by Prof Martin*) in certain parts of Germany the 

 goats of the race of Saanen are especially aff'ected with this complaint. 

 The disease seems to be infectious, for in many villages the miijority of 

 the goats have contracted it whilst in other localities it is unknown. In 

 treating the disease the pustules should be opened and an acaricidal 

 fluid applied. 



BEIEF HISTORICAL ACCOUNT OF THE GEOUP. ^ 



Demodex folliculorum was first seen and mentioned in print b 

 Ilenle in 1841, and was also discovered independently in the following 

 year by G. Simon, of Berlin, who published a good description of this 

 parasite under the name Acarus folliculorum. The generic name 

 Demodex was created for it in 1843 by the celebrated zoologist Richard 

 Owen, the first Director (Superintendent) of the Natural History 

 Museum, South Kensington. Erasmus Wilson's paper on Entozoon 



* See Prof. Martin's useful paper on Demodectic Marge in herbircrous animals, Eev 

 vetcr. (Toulouse), 191?, 70' Ann., Xos. 6, 7. 



