43 



oeconomy, proclaim its existence. But it is customary to take a proof of 

 it yet more direct, from the properties with which the organs of these 

 functions are endowed. We have examined these properties, and we 

 have seen that each of them presents us with, at least, two great modifi- 

 cations; that the last discovers three, which are, voluntary contractility, 

 contractility involuntary and insensible, Stahl's tonic motion ; and 

 lastly, contractility involuntary and sensible, as that of the heart and 

 the intestines. 



If it is useful to analyse, in order to know, it is of equal importance not 

 to multiply causes, from misconceiving the nature of effects; and, if, 

 on the one hand, the multitude of the phenomena of life, inclines us to 

 the belief of many causes to produce them; the unfailing harmony that 

 pervades all the actions, their mutual connexions, and reciprocal depen- 

 dencies, point much more decisively to a sole agent, as causing, direct- 

 ing, and controuling these phenomena. 



The hypothesis of the vital principle, is to the philosophy of living 

 beings, what attraction is to astronomy. To calculate the revolutions of 

 the planets, this science is compelled to recognize a force, which draws 

 them constantly towards the sun, and constrains their tendency to fly 

 from it, within the measured distance of those ellipses, which they de- 

 scribe around that common centre of light and heat, which dispenses to 

 them, as they roll, the precious germs of life and of fertility. We are 

 about to speak of this force, to which all the powers that animate each 

 separate organ, join themselves, and in which all the vital powers are 

 blended, but under the declaration, for the second time, of using the term 

 only in a metaphorical sense. Without this precaution, I might lead you 

 into all the false reasonings, which those have fallen into, who have as- 

 signed to it a real and separate existence. 



The vital power is in perpetual strife with the powers that govern in- 

 animate bodies. The laws of individual nature are, according to the say- 

 ing of antiquity, for ever struggling against those of universal nature ; 

 and life, which is only this contest prolonged, in favour, altogether, of 

 the vital powers, during health, but with uncertain issue in disease, is at 

 an end, the moment in which the bodies endowed with it, fall again into 

 the system of lifeless being. This constant opposition of vital to physi- 

 cal laws, both mechanical and chemical, does not withdraw, altogether, 

 living bodies from the controul of these laws. There are effects always 

 going on in the living being, chemical, physical, and mechanical: only 

 these effects are constantly influenced, modified, and altered by the pow- 

 ers of life*. 



Why, when we stand up, are not all the humours carried down to the 

 lower parts, by the force of gravitation ? The vital power resists the com- 

 pletion of this hydrostatic phenomenon, and neutralizes this tendency of 

 the fluids, the more successfully as the individual is more robust and 

 vigorous. If it is one enfeebled by previous disease, the propensity will 

 be but imperfectly repressed: the feet, after a certain rime, swell; and 

 this oedematous swelling can be ascribed only to the insufficient energy 

 of the vital powers, which determine the distribution of the fluids, &c. 



* In proof of this may be adduced the observation long- since made by Dr. AIEXAJT- 

 DER, that the range of temperature most favourable to the putrefaction of dead animal 

 matter, being between 86 Q and 100 P of Fahrenheit, includes the usual standard of hu- 

 man heat 



