114 FRANCIS DARWIN. 



with a small nerve-trunk running with, the main artery, and 

 with another one accompanying a branch which the artery 

 gives off. 



Cohnheim appears to think that it is necessary for the 

 supply of an artery that there should be ganglion cells 

 situated in the coats of the vessel itself. From what has 

 been said, it will be seen that this is not necessarily the case. 

 The arteries are accompanied by ganglionated nerve-trunks, 

 and the ganglia are sometimes situated on the adventitia, but 

 in that case they do not appear to be more instrumental to 

 the nervous supply of the artery than ganglia which are not 

 so situated. 



There is very little to be said concerning the smaller arte- 

 ries. I have already mentioned that the branches of large 

 arteries are accompanied by ganglionated nerve-trunks, 

 which are connected with the nerve-plexus belonging to the 

 main vessels. Arteries of smaller size are often entwined 

 with delicate, nucleated, nerve-fibres, but I have not been 

 able to trace these fibres to ganglia. 



The veins appear to be very scantily supplied with nerves ; I 

 have only been able to make out, in one preparation, any con- 

 nection between them and ganglionated nerve-trunks. In this 

 preparation there are a small number of ganglia, and a few 

 rather small nerve-trunks ; these form a very irregular 

 plexus, which appears to be connected with two large veins, 

 but not with the artery which accompanies them. A gan- 

 glion is seated on one of the veins, and a trunk arising from 

 it most probably supplies the vein, as it appears to lose itself 

 in the adventitia. 



With regard to Capillaries my observations are more satis- 

 factory; I have distinctly seen delicate nerve-fibres arising 

 from the cells of a ganglion, and supplying the neighbour- 

 ing capillaries, which in some cases form part of the vascular 

 plexus which surrounds the ganglion. 



