199 



arrangement of the ultimate bile-ducts. His figures repre- 

 sent a complete network of intralobular capillary bile-ducts, 

 "svliich may be demonstrated by injection in the livers of the 

 rabbit, amphibia, &c. This network has not yet been de- 

 monstrated in the human liver, as within a few hours after 

 death it is no longer possible to inject the biliary system. 

 Although it is impossible to avoid speaking of these finest 

 bile-passages as capillaries, Hering does not regard them as 

 at all similar in structure to blood-capillaries. The finest 

 passages are without any true wall, being formed merely by 

 the apposition of the grooves which run transversely across 

 the edges of the liver cells ( just so, if two bricks laid side 

 by side in a wall had each of them a vertical groove in the 

 corresponding position, they would form when placed to- 

 gether a vertical channel). These finest channels may be 

 seen to pass into the smallest bile-ducts, which are furnished 

 Avith distinct epithelium, and at the point of junction the 

 epithelial cells lining the duct pass uninterruptedly into liver- 

 cells. His observations have not confirmed those of Biesia- 

 decki, Frey, and others, on the lymphatic sheaths said to 

 surround the capillary blood-vessels of the liver, and he does 

 not regard the existence of such sheaths as proved. Hering 

 has also failed to trace the connection of nerve-fibres with 

 liver cells described by Pfliiger, though he has used the reagent 

 (osmic acid) recommended by him. 



Salia'Ary Glands. — Mayer (Schultze's ^Archiv,' January, 

 1870) has repeated the observations of Pfiiiger on the nerve 

 supply of the salivary glands. His very numerous observa- 

 tions do not permit him to confirm the results of Pfliiger. 

 He was able to discover very few undoubted nerve-fibres in 

 the gland, the greater number of bands and fibres which are 

 seen belonging to the vascular system, though he guards 

 himself against the supposition of imputing to Pfliiger that 

 he has mistaken vessels for nerves. Mayer has never seen 

 any meduUated nerve-fibre penetrate an alveolus of the 

 gland, and the structures which reach the outside of an 

 alveolus are either vessels, or nerves which have lost their 

 medullary sheath. He points out the great improbability of 

 fibres resuming their medullary sheath after having lost it, 

 and further, that it is quite contrary to the general rule that 

 any nerve-fibres should preserve this structure up to their 

 finest terminations. Mayer has seen fine filaments in con- 

 nection with the nuclei or nuclear processes of cells, but 

 entirely failed to obtain any proof that these filaments were 

 nervous. 



Development. — Cazalis ('Archives de Physiologic/ 1870, 



