SCAB IN SHEEP. It is more than probable that the disease is occasioned by neglect. That in ill-kept sheep it quickly assumes a virulent form there is no doubt, since on fat sheep, -or those in the full flush of growth, it is evi dent, as in other farm animals, the parasites can not get control of the body of the sheep. Scab is known by the generally ragged appearance of the sheep, and by bare patches of the skin; by their rubbing the irritated parts, and, if closely exarnined, by reddish, pimply spots, upon which :a small blister or vesicle forms.
The infested sheep also are rest less, and rub themselves against trees and posts to relieve the intolerable itching. Later sore places will be found, the appetite fails, and if relief is not given the animal dies. The mange af fecting the horse, ox, dog, and -cat, depends upon the presence -of insects. There are different insects, known as acan, infesting different animals, having distinct ive characteristics in each, and generally confined to that species of animals; yet the mange from a dog is said to have been com municated to man, and a horse has been infested with mange by means of the skin of a mangy -cat. The sheep acarus does not bore galleries in the skin, but re mains on the surface, clinging to the wool, and finding shelter among the masses of scab pro duced by the drying of exuda tions from the wounds inflicted by these parasites. Experiment has shown that increase of tem perature hastens the hatching of their ova; fourteen days, accord ing to Prof. Brown, of England, sufficed to hatch a lot in a bottle 'carried in the trowsers pocket, while two months' time was re .quired with some kept under glass in a room. The young have six legs; the fully grown, after several changes of skin, have -eight. The microscope reveals numerous sucking-caps or disks iu the legs, enabling the parasite to cling to the wool and skin of the sheep; and renders fully apparent the action of these structures, showing, as the feet advance, how the disks are expanded to grasp the surface of the substance over which the aca rus is moving, apparently retaining their hold in -obedience to the volition of the animal. Thus
itg structure adapts it for crawling over and adhering to the skin, instead of burrowing beneath it. Burrowing acari, like the itch insect in man, are always armed with cutting teeth, set in strong jaws, and their legs are very short. -The body of the female of the sheep acarus is larger than that of the male, rounder in form, the fourth pair of legs are developed nearly as well as the third, and are supplied with terminal slicking disks. The accompanying illustrations represent a female acarus magnified one hun dred diameters, and iL y-oung six-legged acarus, also magnified one hundreu diameters. :Mature mites are visible to the naked eye as pellucid points of the size of a pin's head. Various experiments have been made to ascertain the rapidity of the growth and reproduction of these parasites. The young aeari have been detected in fourteen days from the direct transference of the acarns to the skin of the sheep. In a month the disease had spread over a space of five inches; in ten to twelve weeks pretty nearly over the whole body. A greater or less amount of time may be required under different circumstances of temperature, and other modifying influences.
The first sign of the existence of scab is rubbing against any projecting body within reach; as it extends, sheep bite theniselves, kick with their hind feet at their sides and shoulders. If one is caught and the hand placed on the mouth, while infected parts are scratched, gratification is evinced by nibbling at the hand, and when the infection is severe or general this nibbling move ment is regarded as an infallible sign. Examina tion will disclose spots on the skin, white and hard, the center marked with yellow points of exudation, which adheres to the wool, matting the fibers together The wool may be firm on these spots, and no scabs are seen at this stage.