362 ABDOM1 



The form of the spleen varies very greatly with the varying 

 degrees of distension of the hollow viscera which are related 

 to its visceral aspect. There is good reason to believe that 

 the tetrahedral form which is described above is associated 

 with an empty or only slightly distended stomach and a well- 

 distended intestine. When, however, the stomach is distended 

 and the intestine is more or less empty, the basal surface par- 

 tially or even entirely disappears, and then the spleen assumes 

 a form similar to that of the segment of an orange (Shepherd). 



Structure of the Spleen. -As the spleen will be required when the 

 relations of the left kidney are studied, the dissector should obtain a 

 sheep's spleen for the purpose of studying the structure of the organ. He 

 will find that it is enveloped by two coats (i) serous ; (2) fibro-elastic. 

 The peritoneal investment adheres so closely to the subjacent fibrous coat 

 that it can be removed only with difficulty. With regard to \b& fibro~ elastic 

 tunic (tunica propria), it should be noted that processes, the trabecula of 

 the spleen, proceed from its deep surface and dip into the substance of the 

 organ. The trabeculse constitute the supporting framework of the gland- 

 pulp ; therefore it will be found impossible to strip off the fibrous coat of 

 the spleen without at the same time lacerating its surface. Make a section 

 through the organ, and carry a portion of it to the tap. By squeezing it 

 and allowing the water to run freely over it, the dissector may obtain a 

 view of the trabecular framework. 



Dissection. The sympathetic plexuses in the upper part of 

 the abdomen may now be studied with advantage. Throw the 

 tail and body of the pancreas and the superior part of the duo- 

 denum over to the right. Next, turn to the left cceliac ganglion, 

 which was displayed when the posterior wall of the omental 

 bursa was removed ; it lies between the left border of the cceliac 

 artery and the medial border of the left suprarenal gland (see 

 p. 298). From the medial border of the left cceliac ganglion 

 trace sympathetic nerve fibres across the front of the aorta, 

 round the root of the cceliac artery, to the opposite ganglion, 

 which lies behind the inferior vena cava. To expose the right 

 cceliac ganglion, therefore, it is necessary to displace to the 

 right the portion of the inferior vena cava which lies behind 

 the first part of the duodenum and to fix it out of the way with 

 hooks or pins. Follow each cceliac ganglion upwards and 

 backwards to its union with the greater splanchnic nerve of the 

 same side, and follow the splanchnic nerve to the point where 

 it passes into the abdomen by piercing the crus of the diaphragm 

 of the corresponding side. 



Sympathetic Plexuses. In connection with the sympa- 

 thetic nervous system three large plexuses are formed in front 

 of the vertebral column : they are the cardiac plexus, in 

 the thorax; the coeliac plexus, in the upper part of the 

 abdomen proper ; and the hypogastric plexus, in the lower 

 part of the abdomen proper. 



The cceliac plexus (O.T. solar plexus), which is by far the 



