The SEMINAL VESICLES are very compact glandular structures lying on either side of the median line, on the dorsal side of the bladder, and ventral to the rectum. In the mature bull they measure ten to twelve centimeters in length, four centimeters in width, and about two and one-half to three centimeters in thickness. The glands are distinctly lobulated, quite tortuous, and are often asymmetrical in size and shape. They converge posteriorly, to empty into the urethra at the colliculus seminalis with the ampulla, in a slightly oval slit in the mucosa. Microscopically, the gland is of the anastomosing tubular type, with very poorly developed excretory ducts to the glandular cavities. Posteriorly one finds centrally a few sinus-like narrow excretory passages, which open into the somewhat larger collecting and excretory duct. The epithelium is of the simple columnar type and produces a relatively large amount of secretion. The gland cavities are surrounded by a membrana propria, over which is a relatively thick layer of smooth muscle. Outside this is a connective tissue covering which sends trabeculae or septa in between the lobules. The secretion of the seminal vesicles is a tenacious albuminous fluid with a slightly yellowish tinge, all or part of which appears in the ejaculate in the form of swollen sago-like grains which are soon dissolved following ejaculation and the liquefaction of the semen. The proteid compounds belong to the group of histones. The secretion is liquid when warm and coagulates when cold. Some say that the filling of the vesicles serves to excite sexual feeling, but this is doubtful in view of the fact that in some animals the sexual desire exists before the vesicles are filled. Likewise, Steinach found that rats, whose seminal vesicles had been removed, still retained their desire for copulation. The function of the secretion is to furnish much of the volume to the semen, and in some way it has a distinct bearing on fertility, inasmuch as extirpation of the organs in rats leads to lowered fertility. The vesicles of the bull are in no sense a store-house for spermatozoa, as is usually understood. Repeated examinations in a large number of bulls have led to the finding of spermatozoa there only in very rare instances. That they serve as a resorption place for sperms that are not ejaculated is also very unlikely. Normally, one sees on smear of the vesicles, occasional cells, leucocytes, lecithin granules, sago bodies, and rarely a few degenerated spermatozoa.