General Principles of Physiology. 267 



row. The latter muscles generally excite, or, at least, increase, 

 the action of the bladder and rectum, by pressing them against 

 their contents, and also by this pressure contribute mechanically 

 to expel their contents. Thus, in the above cases, in addition 

 to the failure of nervous influence in the viscera, there is a 

 failure of excitement in the muscles of voluntary motion which 

 conspire with these viscera in certain parts of their functions. 



We can trace the communication of nerves issuing from the 

 great chain of ganglions, placed it would seem^ to facilitate these 

 communications in the centre of the animal system, with all the 

 nerves of the body. Bichat, although his opinions respecting 

 the use of the ganghons are inconsistent with the results of the 

 experiments just referred to, as well as of others to which I shall 

 have occasion to refer, was induced, from their situation and the 

 distribution of their nerves, to regard them as the centres of 

 nervous systems. 



On comparing all the facts on the subject, we have reason to 

 believe, that the system of ganglionic nerves is quite as exten- 

 sive as that of the nerves proceeding directly from the brain and 

 spinal marrow. We every where find blood-vessels which, 

 being influenced equally through the brain and spinal marrow, 

 must receive the nervous influence through the ganglions ; and, 

 indeed we can trace the ganglionic nerves attached to and sup- 

 plying the larger vessels. The following case, related by Dr. 

 Parry, in his treatise on the arterial pulse, might alone be 

 regarded as proving the existence of two sets of nerves in the 

 extremities, the one supplying the organs of voluntary, the other 

 those of involuntary, motion, and strikingly illustrates what 

 has been said on this subject. He observes, " I have seen a 

 total loss of pulse in one arm, with coldness, but complete 

 power of motion in that part while the other arm was warm, 

 and possessed a perfectly good pulse, but had lost all power of 

 voluntary motion." 



Such then is the manner in which the influence of the nervous 

 system is supplied to the muscles of voluntary and involuntary 

 motion. To the former, from certain small portions of the brain 

 and spinal marrow, and through nerves going directly from these 



