Wind-galls are the result of severe work. The back sinews are incased in a fine sheath which contains synovia, or, as it is commonly termed, "joint oil." The use of the synovia is to facilitate the motions of the two great flexor tendons one upon the other; so, when the pace is too fast or the labor too energetic, the delicate membrane which secretes the synovia becomes irritated. The consequence of irritation is increased secretion. More joint oil is poured forth than the natural sac can contain. The membrane, therefore, bags out at those parts which are weakest. Two such places are situated above the fetlock and one below it. The localities, with the size of the tumors, as they generally are exhibited, the reader will find delineated in the following engravings. [Illustration: THE SITUATIONS AND SHAPES OF WIND-GALLS.] [Illustration: WIND-GALLS, AS THEY APPEARED TO THE AUTHOR, UPON DISSECTION.] Wind-galls generally appear on the hind leg. They used to be regarded as swollen bursæ; but Mr. Varnell, Assistant Professor at the Royal Veterinary College, by careful dissection, first pointed out their real character. He proved them to be synovial enlargements; and the writer, benefiting by Mr. Varnell's instruction, has verified the fact. Very slight physiological knowledge was required to detect they were not bursæ. Bursæ are little round sacs, secreting a fluid like synovia, but always placed so as to facilitate motion. Now, wind-galls appear close to a synovial sheath ordained to serve the same purpose. They, moreover, start up in the hollow between the flexor tendons and the suspensory ligament, in which arteries, veins, nerves, and absorbents reside. The merit in discovering they had been misnamed was, perhaps, small; but the credit of demonstrating what they actually were--which demanded a more elevated talent--remains with Mr. Varnell. Wind-galls are fond of the hind leg; or rather, the hinder limbs do the heaviest portion of the horse's work; therefore these deformities are commonly found on those members. There may be one or three on both sides of each leg: they generally are quiescent; but occasionally they prove wind-galls to be something more than the simple blemishes which man is pleased to esteem them. After a hard run it is not unusual to hear a huntsman complain that the wind-galls have disappeared and the back sinews of his hunter have become puffy. When that occurs, the entire sheath suffers excessive irritation, and has enlarged. The horse is then very lame, but a day or two of rest reduces the sudden enlargement, and the animal recovers its soundness. [Illustration: THE DISAPPEARANCE OF WIND-GALLS AND THE PUFFINESS OF THE SYNOVIAL MEMBRANE, PROPER TO THE FLEXOR TENDONS, WHICH ENSUES UPON EXCESSIVE LABOR. ]