120 DR seller's memoir OF THE 



even after its communication by nerves with the nervous centre is destroyed. 

 The onus of proof, therefore, that nervous influence is necessary to maintain the 

 susceptibility of contracting, obviously lies on those who take the affirmative side 

 of the question. Contractility is present to a certain measure in the vegetable 

 kingdom, and in animals destitute of nervous system, whence it may be con- 

 cluded that the organic structure, independently of nerves, is susceptible of the 

 endowment of contractility. If it be said that mere structure cannot assume the 

 vital property of contractility, the answer is, that the difficulty is only thrown 

 farther back by imposing the communicating power on the nervous organism. 

 Such an organ as the heart may be supposed to possess contractility, indepen- 

 dently of its nerves, by its original structure ; but it is not necessary to admit 

 that nothing but phj'sical force is concerned in its production. All the physical 

 forces known to operate in living nature may have been concerned in its de- 

 velopment ; but if from the whole amount of their known efficiency an unsatis- 

 factory solution is obtained, then the residue of force or of direction requisite 

 must be sought for in the potentialities of the reproductive cells derived from the 

 first parents of the species. On this principle only can the development and 

 properties of organic structure be placed. Nor is this view to be rejected as out 

 of the line of physiological evidence. The case is quite parallel to that of the 

 main-spring of a watch. The motive property of such a spring depends on its 

 artificial chemical constitution, and the manipulations necessary to impart to it 

 proper temper ; all these are the effects of ph3'sical forces, directed nevertheless 

 by human intelligence. Thus, even in the effects of a watch-spring, there is pre- 

 sent an effect of the Dixinw inirticAiJa aiirw, which circumstance renders the case 

 quite parallel to the representation given above of the organic structure of the 

 heart. Men do not find watch-springs in nature, but have devised the mode of 

 making them. They have not discovered that the hearts of animals are produced, 

 except as a result of a succession of changes, beginning with the union of the re- 

 productive cells derived from the first parents of every species. "Whence, as 

 there is included in the movement of the main-spring of a watch an element de- 

 rived from human intelligence, so there is, in the contraction of an animal's heart, 

 a something which cannot be identified with the effect of physical force. 



Thus the argument from the necessity of something else than organic structure 

 to account for contractility, used in favour of nervous influence, falls to the 

 ground. Nor indeed was there ever any other strong argument. But, though 

 this part of the subject in dispute between Whytt and Haller has become 

 obsolete, no professed physiologist can wisely omit to study the controversy 

 carried on between two men so distinguished by extent of knowledge and depth 

 of penetration. 



It should be added, that both Unzer and Prochaska took the same side with 

 Whytt, in opposition to Haller, as to the dependence of the muscular structure 



