330 LECTURE XIV. 



cells as such. Still we are just as little able to discern 

 in a gland cell, whilst performing its functions, that its 

 constituent particles are engaged in any peculiar material 

 process, as we were in the case of the nerves, or ciliated 

 epithelium. 



These facts derive great support from the circumstance 

 that we are able to perceive, that the functional activity 

 of individual parts does experience a certain amount of 

 impairment, if it is continued for too long a time. In 

 all parts certain states of fatigue manifest themselves, 

 states, during which the part is no longer able to origi- 

 nate the same amount of movement, that up to that 

 time could be perceived in it. But, in order that they 

 may again become competent to perform their functions, 

 these parts by no means always require a new supply of 

 nutriment, a fresh absorption of nutritive material ; rest 

 alone is sufficient to enable them to resume their activity 

 in a short space of time. A nerve, which has been cut 

 out of the body, and used for experiment, after a cer- 

 tain lapse of time becomes incapable of discharging its 

 functions ; but if it be allowed to repose under favour- 

 able circumstances, which prevent it from drying up, it 

 gradually regains its powers. This restitution of func- 

 tional power (functional restitution), which takes place 

 without any proper nutritive action, and in all proba- 

 bility depends upon the circumstance, that the mole- 

 cules which had quitted their usual position gradually 

 revert to it we can produce in different parts by 

 means of certain stimuli. According to the views of 

 the neuro-pathologists these stimuli would only act 

 upon the nerves, and through the medium of the nerves 

 upon the other parts ; but with reference to this very 

 point we have some facts which cannot well be explained 

 in any other way than by the assumption, that an in- 

 fluence is really exercised upon the parts themselves. 



