100 



ANATOMY AND PHYSIOLOGY OF 



with more detail to the consideration of 

 its constituent parts, such as its coats, 

 nerves and vessels. 



The coats of the horse's stomach having 

 been generally described as four, it appears 

 needless to alter their nomenclature, although 

 the one which I shall allude to as third 

 might quite as justly be described as second, 

 or merely spoken of as connecting cellular 

 tissue, without regarding it as a separate coat. 



The external peritoneal tunic is found 

 proceeding from the diaphragm on to the 

 cardiac portion of the stomach, surrounding 

 the oesophageal opening, where it is tough, 

 and forms the gastro phrenic ligament. Thus 

 we follow it on to the corresponding surface 

 of the viscus, and, firstly, more especially 

 on to the lesser curvature, where it is loosely 

 connected with the other coats, and, the 

 middle portion being more adherent, gives 

 rise to two folds laterally, which seem to 

 stretch from the cardiac to the pyloric orifices, 

 to bind the two together, necessarily leaving 

 a pit or cul-de-sac between them. At the 

 pyloric end the peritoneum comes off from 

 the concave surface of the liver on to the 

 stomach, constituting the gastro-hepatic or 

 lesser omentum, the anterior layer of which 

 comes from the anterior part of the concave 

 surface of the liver, whUst the posterior 

 layer comes from the posterior part of the 

 same, so that the two enclose the vessels 

 going to and from the porta. 



Having formed a covering to the corres- 

 ponding surface of the stomach, the layers 

 of peritoneum meet at the greater curvature. 

 In following them from this point the des- 

 cription will be facilitated by alluding to 

 the two separately, as they meet to form 

 the gastro-splenic and gastro-colic omenta, 

 as well as the omental sac. In forming 

 the latter, they so blend as merely to con- 

 stitute a fine reticulated vascular layer, in- 

 separable into t^vo, except near the magins 

 of the viscera. Distinguishing the anterior 

 or external layer as A, and the posterior or 

 internal one as B, their arrangement admits 

 of exposition in the following terms : — 



A passes from the anterior surface of the 

 stomach, forms the loose omentum, and gets 



on to the transverse colon and spleen. 

 Reaching the latter, it is reflected over its 

 superior surface at the posterior margin of 

 the bilus, so as to contribute to the form- 

 ation of the gastro-spleijic omentum, and 

 extends round the free posterior margin of 

 the viscus on to the inferior surface, passing 

 to the right on to the left kidney, and, 

 anteriorly reaching the supero-anterior part 

 of the spleen, is reflected from it so as to 

 continue as the outer layer of the loose 

 omentum. Further to the right, A is trace- 

 able on to the inferior surface of the trans- 

 verse colon, and, extending round the pos- 

 terior part of the latter, is found to ascend 

 up to the spine, and then turn backward 

 and downward to form the mesentery. 



B, or the internal layer of peritoneum, 

 passes from the posterior surface of the 

 stomach till it reaches the infero-anterior 

 border of the transverse colon, as well as the 

 hilus of the spleen. After covering the an- 

 terior surface of the colon, it ascends up to 

 the pillars of the diaphragm clothing the 

 anterior part of the pancreas, which is thus 

 held between A and B, or layers of the trans- 

 verse meso-colon. A little to the left of this, 

 B passes on to the anterior margin of the 

 hilus of the spleen, forming the inner or pos- 

 terior layer of the gastro-splenic omentum. 



From this arrangement it results that the 

 peritoneum, in forming the lesser or gastro- 

 hepatic, the greater or gastro colic, and the 

 gastro-splenic omenta, closes in a space 

 termed the omental sac, the interior of 

 which is inaccessible except by an opening 

 at the posterior part of the gastro hepatic 

 omentum, whose free margin at the right 

 side marks the point where it may be pene- 

 trated ; this passage is termed the foramen 

 of Winslow. It is bounded anteriorly by 

 the lesser omentum, above by the liver, and 

 posteriorly by the transverse colon. 



Thus, supposing the inner layer of the 

 omental sac to be separable from the outer, 

 and drawn out through the foramen of 

 Winslow, the following parts would be de- 

 prived of peritonaeum, i. e., the posterior 

 surface of the stomach, the gastro splenic 

 omentum of its posterior layer ; so that the 



