PHYSIOLOGICAL ANATOMY OF THE LIVER. 437 



an inch in diameter. They are composed of a delicate membrane, lined with small, flat- 

 tened epithelium. The ducts larger than y^Vs of an inch have a fibrous coat, formed of 

 inelastic with a few elastic elements, and, in the larger ducts, there are, in addition, a few 

 non-striated muscular fibres. The epithelium lining these ducts is of the columnar variety, 

 the cells gradually undergoing a transition from the pavement-form as the ducts increase 

 in size. In the largest ducts, there is a distinct mucous membrane, with mucous glands. 

 Throughout the whole extent of the biliary passages, from the interlobular canals to 

 the ductus choledochus, are little utricular or racemose glands, varying in size in differ- 

 ent portions of the liver, called by Robin, the biliary acini. These are situated, at short 

 intervals, by the sides of the canals. The glands connected with the smallest ducts are 

 simple follicles, from -^ to ^y of an inch long. The larger glands are formed of groups 

 of these follicles, and they measure from ^-^ to -3-^ of an inch in diameter. The glands are 

 only found connected with the ducts ramifying in the substance of the liver, and they do 

 not exist in the hepatic, cystic, and common ducts. They are composed of a homogeneous 

 membrane, lined with small, pale cells of pavement-epithelium. If the ducts in the sub- 

 stance of the liver be isolated, they are found covered with these little groups of follicles 

 and have the appearance of an ordinary racemose gland, except that the acini are rela- 

 tively small and scattered. This appearance is represented in Fig. 133. 



FIG. 133. Anastomoses, and racemose glands attached to the biliary ducts of the pig; magnified 18 diameters. 



(Sappey.) 



moses in arches ; 7, 7, 7, angular anastomoses ; 8, 8, 8, 8, anastomoses by transverse branches. 



The excretory biliary ducts, from the interlobular vessels to the point of emergence 

 of the hepatic duct, present numerous anastomoses with each other in their course. 



Vasa Aberrantia. In the livers of old persons, and occasionally in the adult, certain 

 vessels are found ramifying on the surface of the liver, but always opening into the bil- 

 iary ducts, which have been called vasa aberrantia. These are never found in the foetus 

 or in children. They are, undoubtedly, appendages of the excretory system of the liver, 

 and are analogous in their structure to the ducts, but are apparently hypertrophied, with 

 thickened, fibrous walls, and present, in their course, irregular constrictions, not found 

 in the normal ducts. The racemose glands attached to them are always very much atro- 

 phied. Sappey is of the opinion that these are ducts leading to lobules on the surface of 

 the liver, which have become atrophied. 



Gall-Madder, Hepatic, Cystic, and Common Ducts. The hepatic duct is formed by 



