THE LIVER SECRETION OF BILE. 



621 



stimuli to the Sympathetic nerves FFiK. 227. 



supplying it ; and in some instances 



of obstruction, it has presented an 



appearance very closely resembling 



that of the muscular coat of the 



alimi'ntary canal.* Dr. Davy has 



pointed out, that the mucous coat of 



the Ductus communis is disposed in 



valve-like folds; in such a manner, 



as to prevent the reflux of the bile, 



or of the contents of the intestine. 



826. The Liver may be re- 

 garded as essentially Consist- A vieW f the Ga "- Bladder distended with air, and with its 

 c r ii vessels injected; 1, cystic artery ; 2, the branches of it which 



ing of a mass of cells, in con- supply the peritoneal coat of the liver . 3? the branch of the 



nection With the ramifications hepal i c arte ry which goes to the gall-bladder; 4, the lymphatics 



of the Hepatic Duct : and these O f the gall-bladder.] 

 are in close relation with the 



ramifications of the Portal Vein and Hepatic Artery, that serve to con- 

 vey blood to the minutest parts of this organ ; and with those of the 

 Hepatic Vein, which return it to the heart, after it has been subservient to 

 the Nutrition of the structure and to the elaboration of the Secretion. Be- 

 sides these, the Liver contains Lymphatics and Nerves ; the latter are chiefly 

 derived from the Sympathetic system, and are distributed on the walls of the 

 vessels and ducts. These various portions of the structure are connected 

 together by a fibrous tissue, to which the name of Glisson's Capsule has been 

 given. For our present knowledge of their ultimate arrangement, we are 

 almost entirely indebted to Mr. Kiernan,t whose account of them will be here 

 followed, his researches having been confirmed, in all essential particulars, 

 by other Anatomists. 



a. When a Liver is closely examined with the naked eye, it is seen to be made up of a 

 great number of small granular bodies, about the size of a millet seed, of an irregular form, 

 and presenting a number of rounded projecting 



processes upon their surfaces. These are com- 

 monly termed lobules, although by some Anatomists 

 they are spoken of as acini. When divided longi- 

 tudinally, they have a somewhat foliated appear- 

 ance (Fig. 229), arising from the distribution of 

 the Hepatic Vein ; which, passing into the centre 

 of each division, is termed the in/ra-lobular vein. 

 The exterior of each Lobule is covered by a pro- 

 cess of the capsule of Glisson ; which is very dense 

 in the Pig and other animals ; but which is so thin 

 as to be almost undistiiiguishable in the Human 

 liver. Its substance is composed of the minute 

 ramifications of the before-mentioned vessels, arranged in the manner presently to be de- 

 scribed; the spaces between which are filled up with a parenchyma, composed of nucleated 

 cells, like those shown in Fig. 232. The structure of each lobule, then, gives us the essential 

 characters of the whole gland. 



b. The Lobules, when transversely divided, are usually found to present somewhat of a 

 pentagonal or a hexagonal shape ; the angles being generally somewhat rounded, so as to 

 form a series of passages, or inter-\6bu\a.r spaces : in these lie the branches of the Vena Portae, 

 and of the Hepatic Artery and Duct, from which are derived the plexuses that compose the 

 lobules. Each Lobule, when examined with the microscope, is found to be apparently com- 

 posed of numerous minute bodies of yellowish colour, and of various forms, connected to- 

 gether by vessels , to these the name of acini was given by Malpighi; and to these, if they 

 deserve a name, it ought to be restricted. They will be presently shown, however, to be 

 nothing else than the irregular islets, left between the meshes of the plexus formed by the 

 ultimate ramifications of the Portal Vein. The Vena Portse, it will be recollected, is formed 



[Fig. 228. 



1, Nucleated cells composing the parenchy- 

 ma of the gland; 2, lobules of human liver 

 with ramifications of the hepatic vein.] 



In the Horse and Dog this coat is clearly muscular. 

 Philosophical Transactions, 1833. 



