266 



On the Nerves of the Frog's Lung. 



[Nov. 16,. 



lung are ganglionic cells. More than forty medullated nerve-fibres 

 were counted as they entered the lung, but they were even still 

 more numerous, while in addition there were many non-medullated 

 fibres whose number it was not so easy to ascertain. The main 

 trunks of the nerve were traced into the lung under the serosa, 

 where they give off larger and smaller branches — containing medul- 

 lated and non-medullated fibres — which could be traced across the 

 alveolar wall, giving off finer branches in their course. The main 

 trunks exchange a few nerve-fibres, but the number of fibres so ex- 

 changed is not large. Many of the finer branches, which may contain 

 just one or two medullated fibres, could be traced to the muscular 

 septa of the alveolar wall ; they dip into it, lose their myeline, and 

 form a plexus of non-medullated fibres with elongated meshes. From 

 this plexus finer branches are given off which dip down between 

 the non-striped muscle-cells. The non-medullated nerves join and 

 form a wide-meshed plexus of nerve-fibrils upon the alveolar wall 

 in relation with the thin layer of non-striped muscle which occurs 

 there. From this plexus fibres are given off which seem to form 

 a second plexus with finer meshes. This plexus is quite distinct 

 in its characters from that which occurs in the alveolar septa. Some 

 non-medullated fibres occur on the walls of the blood-vessels. The 

 nerve-cells which occur along the course of the nerve-fibres are 

 verv numerous. They are most numerous where a branch is given 

 off from one of the main trunks, but they also occur along the 

 course of the nerves, it may be at the side or amongst the nerve- 

 fibres, but always within the sheath of the nerve. These nerve- 

 cells present the characters of the cells described by Arnold and 

 Beale, and in the fully developed condition at least are provided 

 with a straight and a spiral process. They are to be found even in 

 the nerve-branches in the apex of the lung. More than three hundred 

 nerve-cells were counted in each lung disposed amongst the nerve- 

 fibres, so that they are relatively far more numerous than the medul- 

 lated nerve-fibres which enter the lung. The arrangement of the nerve- 

 fibres which supply the muscular coats of the arteries and veins are 

 then described and figured. The paper is illustrated by accurate 

 drawings, which show the exact distribution of the intra-pulmonary 

 nerves, the structure of the nerve-cells, and the plexuses of nerve- 

 fibrils which occur in relation with the muscular coat of the lung and 

 the pulmonary blood-vessels. 



