3D 



to which one might feel disposed to assign distinct causes ; but these 

 chemico-vital processes, are so subordinate to sensibility and contractili- 

 ty, that they are met with only in organs endowed with these two proper- 

 ties, and they take place, in a degree more or less perfect, according to 

 the condition of these properties in the organs in which they occur. 



We have stated that there exists two great modifications of sensibility 

 and contractility ; that sensibility is divided into percipient sensibility and 

 latent sensibility ^ that contractility is at times voluntary, at others involun- 

 tary, and that the latter may be perceivable or insensible. 



" Perceiving, (cerebral, nervous, animal, sensib ility, per- 

 ceptibility .} 

 With consciousness of impressions or perceptibility ; 



requires a peculiar apparatus. 

 SENSIBILITY. < Latent, (nutritive, organic sensibility.) 



Without consciousness of impressions; or, general 

 sensibility, common to every thing that has life; it 

 has no peculiar organ, and is found universally 

 . diffused in living parts, animal or vegetable*. 

 'Voluntary and sentient, subordinate to perceptibility. 



CONTRACTILITY. J Involuntary and insensible, corresponding to latent sen- 

 sibility. Tonicity. 

 ^Involuntary and sentient. 

 The cause of this last modification of contractility, appears to depend 

 on the peculiar organization of the system of the great sympathetic 

 nerves. From these nerves, the heart, the digestive canal, Sec. seem to 

 receive the power of exerting sensible contraction, an effect produced by 

 the direct application of a stimulus, and over which volition has no con- 

 troul, as will be stated in speaking of those nerves. 



Sensibility and contractility offer a vast number of differences, the prin- 

 cipal of which depend on the age, the sex, the regimen, the climate, the 

 state of waking or of sleep, health or of sickness, on the relative develope- 

 ment of the lymphatic, cellular, or adipose systems, on the proportions 

 which exist between the nervous and muscular systems. 



In the first place, the principle of sensibility and contractility may, in 

 its action, be likened to a fluid flowing from any source whatsoever, 

 which is consumed, repaired, and drained by use, re-supplied, or exhaust- 

 ed, equally distributed, or, occasionally concentrated on certain organs. 



Secondly. Sensibility, like contractility, is very considerable at the in- 

 stant of birth, and seems to diminish more or less rapidly till death. 



Thirdly. The liveliness and frequency of impressions wear it out very 

 early. It, in a manner, repairs itself, that is, recovers its original deli- 

 cacy, when the sentient organs have been long at rest. Thus, an epicure, 

 whose taste has grown dull with high living, will recover all its accuracy, 

 if during several months, instead of spiced ragouts and spiritous liquors, 

 he lives on dry bread and plain water. In like manner, contractility be- 

 comes exhausted in the muscles which are too long employed, and it is 

 recovered during the repose of sleep. 



Fourthly. The following is an instance of the manner in which sensi- 

 bility becomes concentrated on one organ, and appears to forsake the 



See Note at p. 17. 



