440 A. B. MACALLUM. 



of mau and Necturus. There is besides another justification 

 for narrowing the range of the work as I have done, namely, that 

 one of the highest and one of the lowest Vertebrate types are 

 embraced in the investigation. I do not wish to be understood 

 as believing that the results which I here advance are typical 

 of every "Vertebrate liver. Indeed, the following pages show a 

 not very close agreement of results from the two types, and it 

 would be hazardous to say which presents the form of nerve 

 termination which has the most general occurrence in other 

 Vertebrate livers. 



I may be allowed to insist on one point about which the 

 vaguest opinions are allowed to pass currently as correct : the 

 hepatic cell and nerve-tissue are in close connection, not 

 merely by contact, but by actual union. 



The literature on this subject, what little there is, is full of 

 contradictions or negative statements. Pfliiger, the first 

 observer in this line, came to definite conclusions, it is true, but 

 although experimental physiology has partially confirmed his 

 view, taken as a whole and not in detail, yet the workers since 

 that time who have published descriptions of their researches on 

 the nerves of the liver have found no such connection between 

 these and the hepatic cells as he describes, or, in fact, none at 

 all. The reason for these contradictory results partly is that 

 in nearly every case the researches were based on the Mamma- 

 lian liver, the cellular constituents of which are too small to 

 admit of definitely deciding so difficult a question. 



I proceed now to give a resume of the literature on the sub- 

 ject, coupled with a description of the methods employed in each 

 case. A reference to these methods is necessary in order that 

 I may briefly outline their advantages and disadvantages. 



Pfliiger^ used osmic acid to determine the course of the 

 nerves. He found them rarely single, often in bundles, each 

 single fibre dividing frequently and anastomosing, and finally 

 penetrating the membrane of the liver- cells in order to termi- 

 nate in the latter. The fibres retain their myeline investment 

 up to tlie point of penetrating the cell. The fibres in the 

 1 'Arcbiv fur die ges. Phjsiologie,' ii, 1869, also 1S71. 



