SCABIES IN SHEEP. 



611 



All these solutions, however, are more or less poisonous and need 

 to be used with caution, weak solutions only being used at first, par- 



.>r^^=^ 



Fig. 249. — Adult sheep tick {Melo2)liagus 

 oviniis). (a) Tick ; (6) puparium. Magni- 

 fied. (Salmon and Stiles, Annual Keport, 

 U.S.A. Dept. of Agi-iculture, 1897, p. 103.) 



¥10.250.— Tricho- 

 clectes scalaris 

 of the ox. Mag- 

 nified 20 dia- 

 meters. (After 

 Railhet.) 



ticularly in the case of animals, such as oxen, which are given to licking 

 themselves. 



SCABIES— SCAB— MANGE. 



The term scabies is given to a group of diseases affecting man and 

 all domestic animals. These diseases are produced by two classes of 

 parasites, viz., sarcoptinse, which live within the epidermis or on the 

 surface of the skin, and demodectes {sing, demodex), which penetrate 

 into the sebaceous glands and hair follicles. 



Scabies, though known from the earliest times, has long been con- 

 founded with constitutional diseases characterised by cutaneous erup- 

 tions. The symptoms shown were formerly regarded as due to the 

 elimination of "humours" which the organism was casting off, for 

 which reason scabies was even treated with internal medicines. 



At the present time the cause of the disease is perfectly well under- 

 stood, as well as the mode of development of the different parasites. 

 The rate at which these parasites develop is almost incredible, a fact 

 which explains the highly contagious character of the disease. 



Each species of animal may present several varieties of scabies, 

 caused by different parasites, such as sarcoptes, psoroptes, chorioptes, 

 demodectes, etc. 



SCABIES IN SHEEP. 



Scabies in sheep usually assumes one of three forms — sarcoptic, 

 psoroptic, or chorioptic scabies. Follicular, or demodectic, mange affects 



R K 2 



