534 SPECIAL HISTOLOGY. 



vessels which border upon the hepatic islet, by which they are perfectly 

 filled during life, and will be more thoroughly considered below. 



If, as results from the above analysis, the secreting parenchyma of 

 the liver consists of a solid network of hepatic cells, one cannot but be 

 struck with its great difference from all the other glands of the body ; 

 and the important question arises, how, with this arrangement, the secre- 

 tion is conveyed from the interior of the cells, in which we suppose it to 

 be formed, and finally carried away. Anatomy here gives no sufficient 

 reply ; for although the ramifications of the hepatic ducts have been 

 traced accompanying the vena portce as far as the hepatic islets, yet, as 

 respects the connection of their finest twigs with the hepatic network of 

 cells, no definite answer has been afforded ; and indeed, up to the pre- 

 sent time, no satisfactory account even of the structure of the former 

 has been given. Without entering further, in this place, into the dis- 

 tribution of the hepatic ducts, I will only observe, that in carefully 

 made microscopic preparations, we not unusually find fragments of the 

 finer and finest ducts, the ductus interlobulares of Kiernan, between the 

 hepatic islets, and readily obtain evidence that they are constructed 

 according to the ordinary type of excretory ducts. The minutest of 

 these canals, which I have met with, measured yj^ of a line in diameter, 

 possessed a cavity of 0*0033 of a line, and were composed of a simple 

 layer of common tessellated epithelium-cells, which were distinguished 

 from the hepatic cells by their small size (0-004-0-005 of a line), their 

 pale contents and the minuteness of their nuclei. I have frequently met 

 with such ducts as these ; they had no fibrous coat, perhaps because it 

 had been stripped off in preparing them ; but occasionally they seem to 

 possess a membrana propria, at least their external contours were 

 sharply defined. Larger canals, of 0-04-0*05 of a line, always pos- 

 sessed a coat, and the epithelium was more cylindrical, though not com- 

 pletely so, inasmuch as the cells, with a breadth of 0-0048-0-0056 of a 

 line, measured only 0-006-0-0068 of a line in length. Often as I have 

 sought for a direct communication of the finest canals with the hepatic 

 networks, I have not yet directly observed it ; which is, indeed, by no 

 means surprising, if we consider the softness of the parts with which we 

 have to do ; but unfortunately the result is a hiatus in the minute 

 anatomy of the parts, which can hardly be made good by hypotheses. 

 As such, however, I would offer the supposition, that the finest ducts 

 impinge directly upon the columns of the network of hepatic cells, as 

 the diagram in Fig. 221 shows, so that their cavity is terminated by 

 hepatic cells : and, judging from the scantiness of the finest branches of 

 the hepatic duct, I believe that such communications exist, in no very 

 great numbers, at the circumference of the hepatic islets. 



Whatever view we may take of the connection of the hepatic cell-net- 

 works with the efferent biliary canals, it is undeniable that any such 



