REPORT ON THE PHYSIOLOGY OF THE NERVOUS SYSTEM. 61 



to this globular constitution of the contractile fibre. " Innu- 

 merable very minute but clear and fine parallel lines or striae 

 may be distinctly perceived, transversely marking the fibrillas." 

 Irritability, or the faculty of contracting on the application of a 

 stimulant, is a property inherent in the living fibre. It is an 

 essential element of all vital operations, except of those which 

 have their seat in the nervous system, such as sensation, voli- 

 tion, the intellectual states, and moral affections. All the phe- 

 nomena of life, in the higher animals, may then be ultimately 

 resolved into the single or combined action of these two ele- 

 mentary properties, — irritability and nervous influence, each 

 residing in its appropriate texture and system. 



These preliminary remarks are designed to unfold the prin- 

 ciples to be followed in classifying the vital functions. In ge- 

 neral or comparative physiology, a strictly scientific ari'angement 

 would contemplate first the phenomena of the most elementary 

 life, and would successively trace the more perfect development 

 of those simple actions and their gradual transition into more 

 complex processes, as well as the new functions, superadded 

 in the ascending scale of endowment. But such a mode of 

 classification is wholly inapplicable to the particular physiology 

 of man and of the more perfect animals, viewed by itself and 

 without reference to inferior orders of beings ; for the nutri- 

 tive functions of this class, which correspond with the elemen- 

 tary actions of the simplest vegetable life, are effected by a 

 complex system of vessels and surfaces, deriving their vital 

 powers from contractile fibres, and controlled, if not wholly 

 governed, by nervous influence. It is then manifest, that in 

 the higher physiology the general lav/s of contractility and ' in- 

 nervation' must precede the description of the several functions, 

 which all depend on their single or imited agency. The parti- 

 cular functions will afterwards be classed, as they stand in more 

 immediate relation to one or other of the two essential princi- 

 ples of life. 



In the present state of physiological knowledge, it is impos- 

 sible to determine absolutely, and without an opening to con- 

 troversy, whether the functions of muscle or those of nerve are 

 entitled to precedency. If each were equally independent of 

 the other in the performance of their several offices, the question 

 of priority would resolve itself into one of simple convenience. 

 The actions of the nervous system, if contemplated for the short 

 interval of time during which they are capable of persisting 

 without renovation of tissue, are entirely independent of the 

 contractile fibre. But it is certain that the cooperation of 

 nerve is required in most, if not in all, the actions of the mus- 



