Dept.] NATURAL SCIENCES OF PHILADELPHIA. 17 



As some time will yet elapse before the completion and publication of my 

 next essay on this subject, I wish to give to-night an abstract of the most im- 

 portant points of my researches. It is as follows : 



The parenchyma of the human liver consists of two distinct networks of capilla- 

 ries, with hepatic cells, free nuclei, and granules. These networks of capil- 

 laries are not divided by partitions of fibrous tissue into lobules, but are con- 

 tinuous throughout the whole organ. The meshes which they form are occu- 

 pied by the cells, nuclei, and granules. One of the networks is formed by the 

 ramuscules of the portal vein and hepatic artery, and joins the smallest branches 

 of the hepatic veins. The other commences independently near the smallest 

 branches of the hepatic veins, and is continuous with the finest ramuscules of 

 the hepatic duct, and most probably also with those of the lymphatic vessels of 

 the organ ; so that an injection thrown into the hepatic duct, will return by the 

 latter set of vessels. The capillary vessels forming the last-mentioned net- 

 work I have described in my former paper on the liver, and called ' ' biliary 

 tubules," to distinguish them from the capillaries that carry the blood. 



The whole organ is closely surrounded by a capsule of areolar tissue ; from 

 this, processes are given off which enclose the vessels, ducts, lymphatics and 

 nerves, and thus become their proper sheaths. 



The portal veins, hepatic artery, and hepatic duct, accompanied by lymphatics 

 and nerves, enter the organ in close proximity at its inferior surface ; their lar- 

 ger branches spread out laterally, in a radiating manner, like a fan; some of 

 the vessels, forming the lateral margins of which, run forward, and some 

 backward. The hepatic veins, proceeding from the ascending vena cava, enter 

 the organ posteriorly, and their larger branches run in a postero-anterior di- 

 rection ; but their secondary branches also radiate, and then run almost paral- 

 lel with those of the portal vein and hepatic duct. 



The sheath which surrounds the portal vein, hepatic artery, &c, has usually 

 been known under the name of the "capsule of Glisson;" but as the capsule 

 of the hepatic veins is strictly analogous to it, I shall, for the sake of simplicity, 

 in referring to it, designate it the " capsule of the portal vessels," or "that o 

 the hepatic veins." - * 



Besides the vessels, ducts, lymphatics, and nerves already enumerated' 

 there are in the liver very extensive plexuses, formed by the ducts of racemose 

 glands, which I regard as a special system. This system of glands has been 

 noticed and described to a certain extent by several observers, yet their rela- 

 tionship to the hepatic ducts and lymphatics has to my knowledge never been 

 thoroughly investigated. They are found on the lower surface of the liver, 

 establishing an extensive communication between the larger ducts. They are 

 very abundant on the capsule of the portal vessels, as far as the point where 

 the true interlobular ducts commence, and also exist in the walls of the gall- 

 bladder. The details of this system of glands I shall give in my next essay. 

 For the present, may it suffice to say that their ducts, the diameter of which 

 ranges from l-700th to l-4000th of an inch, anastomose freely with each other 

 and form with branches of the hepatic artery and portal vein (given off within 

 the capsule) a very intricate plexus. From the smallest branches of the lat- 

 ter vessels a capillary rete results, which surrounds the lobules of the glands. 

 Judging from the size of the blood-vessels forming the plexus, the supply of 

 blood to these organs must be very abundant. 



Another set of vessels, or ducts, of a diameter from l-500th to l-2500th of an 

 inch, with single follicular appendages, proceeds from the plexus of racemose 

 glands to communicate freely with the plexus of microscopic lymphatics. 

 These vessels I have also found in the capsule of the hepatic veins. The lobules 

 and larger ducts of the racemose glands are lined by an epithelium of flat 

 hexagonal cells, with large, distinct nuclei, resembling in form and appearance 

 those of the epidermis of the frog. 



1859:] 



