SHEEP HUSBANDRY. 



561 



by contagion. It is very prevalent there, and annually causes an immense 

 loss in the wool and flesh of the British flocks. In the United States it is 

 comparatively little known, and so far as I am able to learn, never origin- 

 ates spontaneously. It is a singular fact that short-wooled sheep, like the 



Fig. 66. ' Fig. 67. Fig. 68. 



THE ACARUS WHICH CAUSES SCAB. 



Fig. 67. — The acari of their natural size on a dark ground. ••, j 



Fig. 66.— The (emalo 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. h. 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 the 

 other parts of the legs are shorter haii-s. To these hairs the young ones adhere, when they first escape 

 from the pustule. 



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

 Fig. 68. — The male on its back, and seen by the same magnifying power. 

 a. — The sucker. 



b. b. b. 6.— Theforelegs with their trumpet-like appendices, as seen in the female. 



c. c. — The two hind-legs, with the same appendices and hairs. 

 d. — The rudiments of the abdominal feet. 



«.— The tail. 



Merino, are much less subject to its attacks, and this is probably one 

 reason for its little comparative prevalence in the United States. Mr. 

 Youatt observes : 



" The old and unhealthy sheep are first attacked, and long-wooled sheep in preference to 

 the short ; a healthy short-wooled sheep will long bid defiance to the contagion, or probably 

 escape it altogether." 



It spreads from individual to individual and from flock to flock, not only 

 by means of direct contact, but by the acari left on posts, stones, and other 

 substances against which diseased sheep have rubbed themselves. Healthy 

 sheep are therefore liable to contract the malady if turned on pastures pre- 

 viously occupied by scabby sheep, though some considerable time may 

 have elapsed since the departure of the latter. 



The sheep laboring under the scab is exceedingly restless. It rubs it- 

 self with violence against trees, stones, fences, &c. It scratches itself 

 with its feet, and bites its sores and tears off" its wool with its teeth. As 

 the pustules are broken, their matter escapes, and forms scabs covering 

 red, inflamed sores. The sores constantly extend, increasing the misery 

 of the tortured animal. If unrelieved, he pines away and soon perishes. 



I have never had an opportunity to observe the post-mortem appear- 

 ances. Mr. Youatt says : 



" The post-mortem appearances are very uncertain and inconclusive. There is generally 

 chronic inflammation of the intestines, with the presf'nceof a great number of worms. The 

 liver is occasionally schirrous, and the spleen enlarged ; and there are frequently serous effu- 

 (1041) .36 



