470 Royal Society : — 



circulation through them under different conditions^ as when they 

 are stretched or compressed. 



The vasa aberrantia in the transverse fissure of the adult human 

 liver are nearer to the branch of tlie portal vein than to the hepatic 

 substance, and can be readily removed without any of the latter. A 

 few small straight branches are sometimes observed to come off from 

 the vasa aberrantia and to enter the hepatic substance. In the foetus, 

 on the other hand, the vasa aberrantia are fewer in number, their 

 course generally is more direct, they lie so close to the hepatic tissue 

 that they cannot be removed unless a portion of the latter is taken 

 away with them, and very many of the branches can be traced into 

 the hepatic substance. 



The author regards the vasa aberrantia in the adult liver in the 

 light of altered secreting tubes, and believes that at one time they 

 formed a part of the secreting structure of the liver. At the termi- 

 nation of intrauterine life the portal vein increases in size, and the 

 pressure thus produced may account for the gradual wasting and 

 partial disappearance of the hej)atic substance closely surrounding 

 it. In the very thin edge of a horse's liver, which consisted prin- 

 cipally of areolar tissue, the gradual alteration of the ducts and 

 ultimate complete disappearance of the secreting cells was traced. 

 Upon the surface of the portal vein in the rabbit's liver the trans- 

 itional stages between the compact lobule of secreting structure and 

 the branches of the vasa aberrantia have been well seen. 



Function of the glands and vasa aberrantia. — It has always been 

 considered that the office of the ducts was to secrete the mucus of 

 the bile, and a similar function was assigned to the vasa aberrantia 

 by Theile. It seems to the author that a cavity communicating 

 with a tube by a neck of less than j-oVo^l^ °f ^'^ ^"^'^ '" diameter, 

 cannot be well adapted for pouring out a viscid, tenacious mucus. 

 If these cavities contained mucus, the injection w'ould not enter 

 them so readily as it does, nor is it easy to conceive how the mucus 

 poured out by these little glands would become thoroughly mixed 

 with the bile as it passes ^long the ducts. Again, the bile of the 

 pig, in which animal these glands are very abundant, does not con- 

 tain more mucus than the bile of the rabbit, in which they are few 

 in number and only found on the largest branches of the duct. The 

 vasa aberrantia do not possess any characters which, in the opinion 

 of the author, justify the inference of their being mucus-glands. He 

 regards the little cavities in the coats of the ducts (glands of the 

 ducts) and the vasa aberrantia as reservoirs for containing bile, 

 whilst it becomes inspissated and undergoes other changes. By 

 these cavities in the ducts with thick walls, the bile is brought into 

 close relation with the vessels which ramify so abundantly upon the 

 external surface of the ducts. 



Of the finest branches of the duct, and of their connexion with the 

 cell- containing network. 



Mammalia. — lu well-injected preparations the smallest branches 

 of the duct can be readily traced up to the secreting cells of the 



