398 TRANSACTIONS OF SECTION D. 



his conception of it in words not very different from Driesch's, when he said that 

 his principle, or agent, was independent of organisation, which yet it animates, 

 sustains, and repairs ; it was the same as Johannes Miiller's conception of an 

 innate ' unconscious idea. ' 



Even in the Middle Ages, long before Descartes, we can trace, if we interpret 

 the language and the spirit of the time, an antithesis that, if not identical, is 

 at least parallel to our alternative between vitalistic and mechanical hypotheses. 

 For instance, Father Harper tells us that Suarez maintained, in opposition to 

 St. Thomas, that in generation and development a Divine interference is postu- 

 lated, by reason of the perfection of living beings; in opposition to St. Thomas, 

 who (while invariably making an exception in the case of the human soul) 

 urged that, since the existence of bodily and natural forms consists solely in their 

 union with matter, the ordinary agencies which operate on matter sufficiently 

 account for them. 3 



But in the history of modern science, or of modern physiology, it is of 

 course to Descartes that we trace the origin of our mechanical hypotheses — to 

 Descartes, who, imitating Archimedes, said, ' Give me matter and motion, and 

 I will construct the universe.' In fact, leaving the more shadowy past alone, 

 we may say that it is since Descartes watched the fountains in the garden, and 

 saw the likeness between their machinery of pumps and pipes and reservoirs 

 to the organs of the circulation of the blood, and since Vaucanson's marvellous 

 automata lent plausibility to the idea of a ' living automaton,' it is since then that 

 men's minds have been perpetually swayed by one or other of the two conflicting 

 tendencies, either to seek an explanation of the phenomena of living things in 

 physical and mechanical considerations, or to attribute them to unknown and 

 mysterious causes, alien to physics and peculiarly concomitant with life. And 

 some men's temperaments, training, and even avocations, render them more 

 pj-one to the one side of this unending controversy, as the minds of other men 

 are naturally more open to the other. As Kiihne said a few years ago at Cam- 

 bridge, the physiologists have been found for several generations leaning on the 

 whole to the mechanical or physico-chemical hypothesis, while the zoologists 

 have been very generally on the side of the Vitalists. 



The very fact that the physiologists were trained in the school of physics, 

 and the fact that the zoologists and botanists relied for so many years upon the 

 vague undefined force of 'heredity' as sufficiently accounting for the develop- 

 ment of the organism, an intrinsic force whose results could be studied but 

 whose nature seemed remote from possible analysis or explanation, these facts 

 alone go far to illustrate and to justify what Kiihne said. 



Claude Bernard held that mechanical, physical, and chemical forces summed 

 up all with which the physiologist has to deal. Verworn denned physiology as 

 ' the chemistry of the proteids ' ; and I think that another physiologist (but I 

 forget who) has declared that the mystery of life lay hidden in ' the chemistry 

 of the enzymes.' But of late, as Dr. Haldane showed in his address a couple of 

 years ago to the Physiological Section, it is among the physiologists themselves, 

 together with the embryologists, that we find the strongest indications of a desire 

 to pass beyond the horizon of Descartes, and to avow that physical and chemical 

 methods, the methods of Helmholtz, Ludwig, and Claude Bernard, fall short of 

 solving the secrets of physiology. On the other hand, in zoology, resort to the 

 method of experiment, the discovery, for instance, of the wonderful effects of 

 chemical or even mechanical stimulation in starting the development of the 

 egg, and again the ceaseless search into the minute structure, or so-called 

 mechanism, of the cell, these, I think, have rather tended to sway a certain 

 number of zoologists in the direction of the mechanical hypothesis. 



But on the whole, I think it is very manifest that there is abroad on all 

 sides a greater spirit of hesitation and caution than of old, and that the lessons 

 of the philosopher have had their influence on our minds. We realise that the 



' Cum formarum naturalium et corporalium esse non consistat nisi in unione 

 ad materiam; ejusdem agentis esse videtur eas producere, cujus est materiam 

 transmutare. Secundo, quia cum hujusmodi formae non excedant virtutem et 

 ordinem et facultatem principiorum agentium in natura, nulla videtur necessitas 

 eorum originem in principia reducere altiora.'— Aquinas, De Pot. Q. iii., a. 11; 

 Cf. Harper, Metaphysics of the School, iii. 1, p. 152. 



