872 



DISEASES OF THE SHEEP. 



a female it appears with a multitude of young. These im- 

 mediately set to work on the skin, bury themselves and prop- 

 agate until the poor animal is irritated to death, or becomes 

 incrusted with scab. M Walz satisfactorily traced the par- 

 asite through all its changes, and by experiment discovered 

 its mode of action, and method of infection. He found that 

 when the male acari was placed on a sheep it burrowed, the 

 pustule was formed, but the itching and scab soon disappear- 

 ed without the employment of any remedy. Such was not 

 the case where the female acari was placed on the sound 

 skin ; as with the breaking of the pustule from eight to fif- 

 teen little ones made their appearance. M. Walz found that 

 the young acari kept in a dry place, dried and crumbled to 

 dust ; but when old, that it would retain its life through the 

 whole winter ; thus proving the necessity of not relying on 

 the season for their destruction, but on preparations of active 

 medicine when the disease shows itself. Of the origin of 

 these insects, we of course can know nothing ; it is enough 

 that we are certain when they make their appearance they 

 can be met and destroyed." — [Cultivator.) 



Fig. 3. 



Fi? 1. The insects of their natural size on a dark ground. 



Fig. 2. The fbniale, of 366 times the natural size, larger than the male, of an 

 oval form, and provided with eight feet, four before and four behind. 



a. The sucker. 



b. b. b. b The four anterior feet, with their trumpet-like appendices. 



c. c. The two interior hind-feet. 



d. d. The two outward feet, the extremities of which are provided with some 

 long hairs, and on other parts of the legs are shorter hairs. To these hairs the 

 young ones adhere when they first appear from the pustule. 



e. The tail, containing the anus and vulva, garnished by some short hairs. 

 Fig. 3. The male on his back, and seen by the same magnifying power. 



