146 THE INVOL UNTAR Y NER VO US S YSTEM 



borate) causes well-marked acceleration when applied to the 

 longitudinal blood vessel. 



He has also discovered another remarkable characteristic 

 in connexion with the adrenaline in these cells ; if the living 

 ganglion is stained with methylene blue, the ganglion cells and 

 their processes take on a blue coloration, the number and posi- 

 tion of the cells thus coloured varying in different experiments ; 

 this coloration is not permanent but soon begins to fade. If 

 however a solution of a chrome salt be inserted under the cover 

 slip when the blue coloration is most distinct, then all the cells 

 and nerve fibres decolorize almost immediately with the excep- 

 tion of the three cells containing adrenaline, which remain blue 

 and are still blue even on the next day. Ultimately they too 

 lose their colour. This more permanent blue coloration is not 

 confined to the nerve cell but extends some distance along the 

 axon of the cell. The reaction is evidently dependent on the 

 presence of adrenaline, and it shows therefore that the adrenaline 

 is not confined to the body of the cell, but extends into the axon 

 as well. 



In the case of the medullary cells of the suprarenal gland, 

 the adrenaline is discharged from the cell into the surrounding 

 fluid by the action of fibres of the splanchnic nerve ; it is just 

 possible that in the case of the leech the adrenaline passes from 

 the cell to the periphery by way of the motor nerve itself. If 

 such a suggestion prove to be true it opens out a new and most 

 important chapter in our conceptions of the nature of nervous 

 action. 



Of equal or even greater importance for neurology is the dis- 

 covery that one nerve cell sends a nerve fibre into each of two 

 separate outgoing nerves by means of a splitting of its axon 

 within the central nervous system. A similar supply of two 

 nerve fibres from a single cell to separate nerves is indicated also 

 in the Crustacean central nervous system, so that such an innerva- 

 tion appears not to be uncommon among invertebrates. In the 

 same invertebrates the motor nerves to muscles of one function 

 seem to run in a separate nerve from those to the antagon- 

 istic muscles ; thus Hardy's work showed that in the Crustacean 

 the motor nerves to the flexors were grouped in one nerve and 

 those to the extensors in another ; and my son finds that stimula- 

 tion of the anterior nerve in the leech causes contraction of the 



