lyS THE HISTORY OF BIOLOGY 



the blood, besides which the inhaled air conveys to it fresh ether particles, 

 which augment its power to keep the mechanism of the body working. It 

 would take too long to record here the complicated accounts of the produc- 

 tion and dispersion of the nervous fluid; it may just be mentioned that the 

 finest and most vitally essential part of the fluid is said to emanate from the 

 cortex of the great brain. The male semen is closely akin to the nervous fluid, 

 and its function is thus to give life to the egg, so that it may start developing. 



Hoffmann, having thus described the mechanism of the body, declares 

 that man naturally possesses an immortal soul, given him by God; the will of 

 this soul controls the movement of the body, and through it we understand, 

 think, and act. Following many other old authors and supported by the Holy 

 Scriptures, he divides man into three "principia" — namely, corpus, spiritus, 

 and anima — that is, the body, the above-described nervous fluid, and the con- 

 sciousness. But besides these man possesses a higher "substance," which the 

 ancient philosophers called mens and which Scripture names the image of 

 the spirit of God; this substance makes use of the consciousness's impression 

 of things and forms them into ideas; false sense-impressions may be rectified 

 by clear reason, but a mass of confused sense-impressions causes madness. 

 Concussion of mind may also disturb the circulation of the blood and produce 

 a condition of sickness in the body. But Hoffmann resolutely denies that 

 the movement and function of the body originate in the soul; "although the 

 human soul possesses a certain limited influence over the bodily parts, never- 

 theless medicine both in theory and in practice is pure mechanics, in that it 

 is based upon purely mechanical principles — namely, motion and matter." 

 The inconsistencies and the arbitrary constructions of thought in this attempt 

 to form a mechanical conception of life-phenomena will be easily realized by 

 the modern reader, but should not in any way detract from the respect due 

 to this attempt — which at any rate is based on very substantial experiences, 

 considering the age — to find a natural connexion in the life-process. The 

 assumption of an immortal soul is explained by the fact that Hoffmann was 

 a devout Christian with a markedly pietistic temperament; Halle was the 

 source and centre of pietism, and Hoffmann was a warm friend of its founders, 

 Spener and Franke. He also displays in many places a naive childlike piety, 

 as when he dedicates one of his books to "The Holy Trinity, the Supreme 

 Physician." Thus we have here a proof that a mechanical conception of life 

 and ancient theological dogmas were formerly capable of being reconciled, 

 which would hardly be considered possible in our own day. 



One of Hoffmann's first steps when elected professor at Halle was to 

 bring about the appointment of an old fellow student from Jena, Georg 

 Ernst Stahl, to be assistant professor of medicine; Hoffmann retained for 

 himself the position of teacher in practical medicine, while Stahl took over 

 the theoretical side. Stahl was born in 1660 of a Protestant family at Ansbach 



