466 



DISSECTION OF THE ABDOMEN. 



Fig. 157. 



The trabecular tissue (fig. 157) forms a network through the whole in- 

 terior of the spleen, similar to that of a sponge, which is joined to the 

 external casing, and forms sheaths around the vessels. Its processes or 

 threads are white, flattened or cylindrical, and average from T ^th to ^th 

 of an inch : they consist of fibrous and elastic tissues, with a few muscular 

 fibres. The interstices communicate freely together, and contain the 

 proper substance of the spleen, and the vessels. 



Microscopic appearances. The characters of the spleen substance can- 

 not be ascertained without the aid of the microscope. 



The splenic pulp is a soft red-brown mass, which is lodged in the areolae 

 of the trabecular structure. Under the microscope this material is seen 

 to be composed of a fine network of ramifying 

 connective tissue corpuscles, with blood-cells in its 

 meshes. 



The Malpighian corpuscles are small rounded 

 whitish bodies, about ^' ff th of an inch in diameter, 

 and are connected w T ith the outer coat of the 

 smallest branches of the arteries ; they project 

 into the pulp of the spleen, and are surrounded by 

 it. In structure they are like the lymph follicles 

 of the intestine, consisting of reticular tissue, with 

 lymph corpuscles in its meshes, through which 

 blood-capillaries pass. 



Bloodvessels. The larger branches of the splenic 

 artery are surrounded by sheaths of fibrous tissue 

 in the trabeculse ; but the smallest branches leave 

 the sheathing, and break up into tufts of capil- 

 laries, which open into the fine meshes of the 

 spleen substance. In the smallest branches, with 

 which the Malpighian corpuscles are united, the 

 outer coat is thickened by lymphoid tissue, and is 

 directly continuous with those bodies in structure. 

 The splenic rein begins in the meshes of the 

 splenic pulp by open channels. From the union 

 of these radicles arise small branches, which unite 

 into trunks larger than the accompanying arteries, 

 and issue by the fissure of the spleen ; in their course they receive acces- 

 sory branches, some joining at a right angle. 



Nerves and lymphatics. The lymphatics are superficial and deep, and 

 enter the glands in the gastro-splenic omentum. In the spleen they begin 

 in the corpuscles of Malpighi, and in the outer coat of the smallest arteries ; 

 they are conveyed to the hilum of the spleen on the vessels. The nerves 

 come from the solar plexus, and surround the artery and its branches. 



A DRAWING OF THE TRA- 

 BECITLAR STRUCTURE OP 

 THE SPLEEN OF THE Ox, 

 at some distance from the 

 hilum. 



THE LIVER. 



The liver secretes the bile, and is the largest gland in the body. Its 

 duct opens into the duodenum with that of "the pancreas. 



Dissection (fig. 158). Preparatory to examining the liver, the vessels 

 at the under surface should be dissected out. This proceeding will be 

 facilitated by distending the vena cava and vena portae with tow or cotton 

 wool, and the gall-bladder with air through its duct. The several vessels 

 and the ducts are then to be defined, and the gall-bladder to be cleaned. 



