DISEASES OF SHEEP. 361 



a rule is based on the same principle, "let others do it." But if 

 all concerned were actuated let us say by common sound sense, 

 this disease might be exterminated utterly in a few years; the 

 greatesj; difficulty being experienced in the first three from the 

 beginning. After that the work would be easy and more and 

 more effective, as the numbers of the pests became reduced. But 

 under present circumstances, in which the rule seems to be how not 

 to do it, the pestilence yearly becomes more and more extended, 

 and relief fades into the uncertain distance. Thus the shepherd is 

 under the necessity of dipping his sheep twice a year and still 

 with only negative results. 



The habits of this insect are similar to those of the previously 

 described one. The first symptoms of its presence are that the 

 sheep are seen to be biting themselves, apparently nibbling the 

 wool. This of itself is bad, for the wool is apt to be swallowed 

 and gathers in the intestines where it forms balls, which by ac- 

 cumulation of mucus and more wool, finally obstruct the intes- 

 tines and cause trouble which is most likely to end fatally. This 

 is one of the results of this infection which otherwise would not 

 happen. The fleece of a scabby sheep soon becomes rough, ragged, 

 and matted in patches, these spreading until in time they meet, 

 when the animal exhibits the wretched appearance showed at fig. 

 27. At this stage of the disease, the crusts have greatly increased 

 in thickness, and are more firmly adherent to the body. These 

 crusts, in the same manner as some of the vegetable growths 

 like ringworm, spread from the outer edge, and thus continually 

 grow larger, while the centers heal, but leave the bare skin. 

 If the inflammation has penetrated to the wool follicles of the 

 skin, in which the fibers are rooted, these spots will remain per- 

 manently bare, rough, and unsightly. 



In those places in which the fleece still exists, it is stuck to- 

 gether in rough masses, tangled and matted, felted in fact, and 

 and thus the sheep in its efforts to relieve itself from the intolera- 

 ble irritation, tears off the wool, leaving bare spots, not as yet 

 so far been diseased, but only as to form scabs, but yet so far as to 

 loosen the wool. This species is most inclined to the thickest 

 and longest wool, and hence it does the most damage to the 

 flock owner. The disease begins on the back, spreading to the 

 rump and down the flanks. The scabs are at first separated ; as 

 the disease spreads from the centers first infected; but in time 

 these spots run together leaving between the active centers bare 

 patches in thickened skin. At the edges of these patches the in- 

 sects are found in the greatest numbers, and entirely cover the 

 skin. They may there be seen moving in large clusters, and if 

 picked up and placed on the hand their motions are easily visible. 

 Old and young of each sex, in the act of propagating, and the 

 eggs, may all be gathered in this way for observation by the 

 curicus. 



The disease is at its worst in the Fall and Winter. As may be 

 thought the poorly nourished and exposed flocks suffer the mot 

 because of their want of ability to resist, and the disease will 



