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TEE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



Descartes gives a metaphysical definition of the 

 soul and a physical definition of life. The soul is 

 that higher principle which makes itself known 

 by thought ; life is merely a higher result from 

 mechanical laws. The human body is a machine, 

 made up of springs, levers, pipes, filters, sieves, 

 and squeezers. This machine is made only for 

 itself; the soul unites with it only for the con- 

 templation of whatever takes place in the body 

 as a mere spectator, but it takes no part what- 

 ever in the discharge of vital functions. The 

 ideas entertained by Leibnitz, as regards their 

 physiological character, are closely analogous to 

 those of Descartes. He, too, like Descartes, sev- 

 ers the soul from the body, and, though he admits 

 a harmony preestablished between them by divine 

 power, he denies that they have any sort of re- 

 ciprocal influence. " The body " — these are his 

 words — " goes on in its development mechanical- 

 ly, and the laws of mechanics are never trans- 

 gressed in its natural motions ; everything takes 

 place in souls as though there were no body, and 

 in the body everything takes place as though 

 there were no soul." 



Stahl's conceptions of the nature of vital phe- 

 nomena and the relations between soul and body 

 were totally unlike these. In considering the ac- 

 tion of life, he throws aside all explanations which 

 would apply alike to such action and to the me- 

 chanical, physical, and chemical phenomena of 

 inert matter. An eminent chemist himself, he 

 assails with great power and peculiar authority 

 the extravagances of the chemist-doctors, or iatro- 

 chemists, men like Sylvius de Le Boe, Willis, and 

 others, who resolved all the phenomena of life 

 into chemical action, fermentations, alkalinities, 

 acidities, and effervescences. He goes further than 

 to maintain that chemical forces are different 

 from the forces that rule the manifestations of 

 life, and even asserts that the former are hostile 

 to the latter, and that they tend to the destruc- 

 tion instead of the preservation of the living body. 

 We must have, as Stahl teaches, a vital force that 

 protects the body against the action of external 

 chemical forces which press incessantly toward 

 its attack and destruction ; life is the triumph of 

 such vital forces over the others. Stahl was led 

 by these ideas to his theory of vitalimi ; but he 

 did not stop at that stage : it was but a first step 

 in the path that led him at last to animism. This 

 vital force, he says, struggling without rest against 

 physical forces, acts intelligently, upon a definite 

 plan, for the preservation of the organism. But 

 if vital force is intelligent, why make any distinc- 

 tion between it and the rational soul? Basil Va- 



lentin and Paracelsus, his disciple, had imagined 

 the existence in infinite number of immaterial in- 

 telligent principles, the archcea, which governed 

 the phenomena in the living body. Van Helmont, 

 the most famous representative of these archceic 

 teachings, who joined a genius for experiment to 

 an imagination wholly ungoverned in its starts 

 and sallies, dreamed out a whole hierarchy of 

 these immaterial principles. Highest of all was 

 placed the rational and immortal soul, undis- 

 tinguished from God ; next the sentient and mor- 

 tal soul, using as its agent another chief of the 

 archcea, which in its turn controlled a multitude 

 of subordinate archcea, styled the bias. Stahl, 

 following Van Helmont a century later, and car- 

 rying on his ideas, reduces all these notions of 

 intelligent principles, governing or archceic spirits, 

 to some simplicity. He acknowledges but one 

 soul, the soul immortal, charged also with the 

 control of the body. He regards the soul as the 

 very principle of life. Life is one of the soul's 

 modes of action, it is the soul's vivific act. The 

 immortal soul, an intelligent and rational force, 

 rules directly the matter of the body, sets it at 

 work, guides it to its end. It is this soul which 

 not merely commands our voluntary acts, but 

 which, moreover, sets the heart beating, sends the 

 blood on its course, lifts the lungs in breathing, 

 makes the glands secrete. If the unison of these 

 phenomena is disturbed, if disease occurs, it is 

 because the soul has failed to discharge its func- 

 tions, or has not succeeded in effectual resistance 

 to external causes of destruction. A doctrine 

 like this contained singular contradictions, since 

 the influence of a rational soul upon vital pro- 

 cesses seems to imply conscious direction, while 

 the simplest observation teaches us that all the 

 functions of nutrition, circulation, digestion, se- 

 cretions, etc., are unconscious and involuntary, as 

 if, to borrow the phrase of a physiological phi- 

 losopher, Nature had chosen, out of caution, to 

 withdraw these important processes from the con- 

 trol of a capricious and ignorant will. So that 

 the animism of Stahl was stamped by an extrav- 

 agance that induced his successors, if not to give 

 it up, at least to subject it to very grave modifica- 

 tions. 



Descartes's ideas, and those of Stahl, left a 

 deep impression on science, and set two currents 

 in motion, which have continued flowing even to 

 our own day. Descartes laid down first princi- 

 ples, and applied mechanical laws to the action 

 of that machine, the human body. His pupils 

 gave breadth and precision to mechanical expla- 

 nations of the various vital phenomena. Among 



