General Pritlciples of Physiology. 273 



capable of being stimulated by the same influence which operates 

 in the formation of the secreted fluids. The increase of secret- 

 ing power in any part would be in vain, were there not at 

 the same time a corresponding increase in the supply of 

 the fluids on which it operates. A similar observation ap- 

 plies to the excretory muscles, as far as they are mus- 

 cles of involuntary motion. The same increase of nervous 

 influence which occasions an increased flow of secreted fluids, 

 excites these muscles to carry off" the increased quantity. 

 Nature does not seem to trust this to the increase of stimulus, 

 occasioned by the increased flow of the secreted fluid, which 

 we have reason to believe from the modus operandi of certain 

 causes of inflammation, would often occasion morbid distention. 

 Now the vascular system, and the muscles of excretion, if in 

 them we include the alimentary canal, comprehend all the 

 muscles which are supplied with ganglionic nerves, unless we 

 regard the iris as a muscle. The state of this organ is quite 

 anomalous in the animal economy, being one of involuntary 

 motion, excited only through the medium of the nervous system. 

 In the preceding view of the subject, we find the relation of 

 the vessels of secretion to the nervous system the same as that 

 of the heart and vessels of circulation. Their function is inde- 

 pendent of, but capable of being influenced by, this system. 



Thus, we perceive, the necessity of every part of the function 

 which the ganglions appear to perform. A combination of the 

 whole nervous influence is necessary to the due formatioitof the 

 secreted fluids; and that there may be, under all circumstances, 

 both a due supply of the fluids to be acted upon, and a due re- 

 moval of those prepared, whether for the functions of life, or for 

 the purpose of being thrown out of the system, it is necessary, 

 as appears from what has just been said, that the powers which 

 convey all these fluids should be subjected to the influence by 

 which secretion is performed. This function, it is evident, 

 requires a more regular supply of fluids than could have been 

 obtained, had the usual action of the vessels depended on the 

 nervous system, which is subject to continual variation ; but 

 had not this system been capable of influencing the vessels, not 



