4SG Till-: AXATO.MY OF THE HORSE 



THE SPLEEN 



TriK SPLKKV can scarooly he foiisidt-rcil jis a .inland, ina-^mucli as it has no 

 excretory duct, but it contains within its substance a number of little bodies, 

 called .Aial]>i.<,diian corpuscles, which most probably perforni the same oiKce 

 as the absorbent glands. Its weight as compared with the whole bod}' is 

 about the same as in man, whose spleen weighs six ounces, wliile that of the 

 horse rarel}' exceeds three pounds. It is attached by the lesser omentum 

 (a fold of the peritoneum) to the stomach (see Fig. 77, page 481), and occupies 

 tlic left side of that organ. It is covered by a serous coat continuous with 

 the peritoneum, and its internal structure is spongy, and made up of cells 

 which contain a large quantity of blood. 



Tjik fuxctiox of the spleen is not positively ascertained, but it is believed 

 to perform the ollice of a reservoir for the blood reipiired by the stomach, 

 witli which it is closely connected by a set of vessels (vasa brevia), and 

 also to effect some change in the blood itself. 



THE PANCREAS 



TiiK PANCREAS IS an elongated gland resembling in structure the salivary 

 o-laiids, placed close to the spine, above the stomach. It has two excretory 

 ducts, which carry the pancreatic lluid secreted by it into the duodenum 

 through a valvular opening common to it and the hepatic duct. The use of 

 the pancreatic fluid appears to be similar to that of the saliva. 



THE KIDNEYS 



TiTE KIDNEYS are two oval organs situated beneath the psoas muscles, and 

 only retained in their position by the fatty cellular membrane which en- 

 velops them, and by the upward pressure of the other abdominal viscera 

 below them. The right kidney is completely within the ribs, but the left 

 scarcely advances at all beyond the eighteenth rib : each averages about 

 forty ounces in weight, but there is a considerable variation in size and 

 form. Unlike the corresponding organ in the cow, the horse's kidney is 

 not split up into lobules, though there is some little irregularity of outline 

 and surface, as may be seen in the annexed figure, which was taken from a 

 .specimen somewhat remarkable in these respects. A transverse section 

 sliows the internal structure, which is composed of a central cavity, the 

 pelvis, into which the urine flows, and from which it is carried to the bladder 

 by the ureter. In this pelvis several conical projections are visi\:)le, having 

 minute openings around their apices, which are the terminations of the 

 tubuli uriniferi composing the substance of the internal part of the organ. 

 The external is the true secreting portion, and in this are contained a 

 multitude of minute red globular bodies, composed of a flexus of capillary 

 vessels, and of a coil of tube in connection with the uriniferous tubuli, both 



