DISEASES OF SHEEP. 359 



the progeny of a single mite may number a full million. Figures 

 fail to convey the desperate condition of an unfortunate sheep 

 on which only a few of these mites are existing at the outset of 

 a Summer. The picture of a scabby sheep here given, affords 

 some approximate idea of the condition of the animal unless re- 

 lieved of the millions of these insects which are burrowing under 

 the diseased skin, covered by these filthy sores, as described in 

 the above quotation. 



If any inquiring reader will take a piece of this dry scab from 

 one of these sores, and lay it on a piece of white paper under a 

 common magnifying glass, the insects may be seen moving like 

 so much dust on the sheet. When more highly magnified the 

 insect appears much like a spider, to which it is somewhat re- 

 lated, as may be seen in the engraving below which shows the 

 mature insect. 



THE HEAD SCAB MITE AN ADULT FEMALE. 

 SARCOPTES SCABICI, VARIETY OV1S. 



The head mites infest the skin of the sheep's head, beginning 

 at the lips, near the nostrils, and eyelids and ears. From these 



points they spread over the face 

 and even down to the fore legs, 

 under the belly and back of the 

 knees, where the wool is short. 

 These pests go into the long wool, 

 or the coarse fine oily kinds, but 

 prefer the short, dry fleece to 

 work in. 



The first indication is the rub- 

 bing of the head by the sheep, 

 FIG. 28.-Highly Magnified. and the extent of the i nvas i on is 



to be judged by the efforts of 



the sheep to rid itself of its tormentors. At first there are slight 

 elevations of the skin with soft centers, which break of them- 

 selves, and discharge a thin fluid which dries and forms hard 

 scabs, which adhere to the skin and the hairs. In these shelters 

 the insects feed, produce their young, and increase in number. 

 As this increase makes it necessary these spots spread until the 

 skin is covered with scabs, which increase in size and thickness, 

 forming white, hard masses. In time they cover the face, lips, 

 and forehead, and as the sheep rub themselves these scabs are 

 broken and bleed. In time the wounds heal and scars are formed. 

 At times the eyes are completely covered by the scabs, and the 

 sheep becomes blind and helpless. 



Infection occurs from sheep to sheep, thus spreading through 

 the flock. There is no other way by which these insects propa- 

 gate or originate, but the ordinary process of generation from 

 parents to offspring and so on through succeeding generations. 

 Thus the only way to find relief is to destroy the insects, thus 

 cutting off the parents and stopping the increase. There are 

 necessarily several ways of this infection spreading. The insects 



