430 NERVOUS SYSTEM. 



not remain indefinitely, after the cerebro-spinal branches 

 have been divided. It remains, however, to apply these ex- 

 periments to other sympathetic ganglia ; but, in the case of 

 the snbmaxillary, they are very satisfactory, from the facility 

 with which the parts may be operated upon, and the certainty 

 with which the ganglion may be separated from its connec- 

 tions with the cerebro-spinal system. As regards the ex- 

 planation of the final loss of power over the functions of the 

 snbmaxillary gland, the experiments of Waller seem to have 

 escaped the attention of the eminent physiologist whom we 

 have quoted. There is no experimental fact more conclu- 

 sively demonstrated than that of the anatomical degeneration 

 and consequent loss of physiological function of nerve-fibres 

 in a few days after they have been separated from their cen- 

 tres of origin. After division of a cerebro-spinal nerve-trunk, 

 the tubes soon lose their anatomical characters, and will no 

 longer respond to a galvanic stimulus. In the case of the 

 fibres operating upon the submaxillary gland, the question 

 of their degeneration after division of the cerebro-spinal 

 roots was not submitted to microscopical investigation. If 

 these fibres had undergone the degeneration which has so 

 frequently been observed in experiments upon other nerves, 

 their galvanization would not have produced any effect ; 

 which was precisely the result obtained by Bernard. In the 

 absence of direct observations upon this point, it is the most 

 reasonable view to adopt, that the fibres from the cerebro- 

 spinal nerves had lost their function, as a natural consequence 

 of separation from their centres, and that this was the cause 

 of the absence of effect upon the gland following their gal- 

 vanization. The observation of Bernard shows, however, 

 that filaments may pass to special organs from the cerebro- 

 spinal centres through the sympathetic ganglia. 



Functions of the Sympathetic System. 



In the earfy part of the last century (1712 and 1725), 

 Pourfour du Petit demonstrated that the influence of the 



