ELASTICITY. 



57 



tory these two properties were looked upon as 

 identical ; that even the illustrious Cullen has 

 scarcely distinguished them, and that some of 

 our most eminent living physiologists have 

 fallen into manifest errors upon the same sub- 

 ject, it becomes plain that we cannot be too 

 particular in familiarizing ourselves with the 

 distinctions between these totally independent 

 forces. 



It is not enough to say that contractility is 

 a vital and elasticity a physical property; for 

 as we are ignorant alike of the nature of life 

 and of elasticity, a distinction founded upon 

 any such assumption must necessarily be futile. 

 It is only by a diligent comparison of their 

 respective laws that we can assign to each its 

 proper limits. Let us then observe in con- 

 trasting them, first, that elasticity can never 

 act as a prime mover; it is never a source of 

 power, but merely the reaction of a force pre- 

 viously applied : thus, the elasticity of the 

 spring will never of itself set the watch in 

 motion unless some external force shall, in the 

 first instance, have acted upon or bent it. But 

 contractility can of itself originate motion, at 

 least it is not essential that any mechanical 

 force with which we are acquainted should 

 precede its action. Again, the force of elas- 

 ticity can never exceed that other power which 

 has called it into existence; if, for instance, 

 a weight of one pound be required to depress 

 an elastic spring, the force of reaction upon 

 the removal of that weight can never exceed 

 the measure of a pound. But, in the case of 

 muscular contraction, there is no such limit; 

 there is no fixed ratio between the cause and 

 the effect ; the slightest touch of a sharp in- 

 strument will, in an irritable muscle, such as 

 the heart, excite the most violent contractions. 

 Elasticity cannot manifest itself except by the 

 removal or suspension of the cause which has 

 called it into action : muscularity requires no 

 such suspension of its exciting cause. The 

 exciting cause of elasticity is always of a phy- 

 sical nature ; but many other causes no ways 

 allied to physical ones may excite the muscular 

 power. Lastly, elasticity is not destroyed by 

 death nor affected by opium or other narcotics, 

 while contractility presents a very striking con- 

 trast in both these respects. 



These facts are quite conclusive in proving 

 that muscular and elastic contraction are go- 

 verned by distinct laws, and cannot conse- 

 quently be referred to the same source. But 

 if some physiologists have erred in overlooking 

 the distinctions between these two properties, 

 if they have not analysed with sufficient care, 

 others have unquestionably erred in an oppo- 

 site direction, and by pushing analysis too far, 

 have attributed to imaginary forces effects 

 which are the result of elasticity alone. We 

 feel much diffidence in controverting any doc- 

 trine supported by the genius and authority 

 of Bichat, but we confess that the distinction 

 which that celebrated anatomist is so anxious 

 throughout his various works to establish be- 

 tween what he terms " contractility of tissue" 

 and elasticity, appears to us unfounded. Elas- 



ticity according to him is a purely physical 

 property. Contractility of tissue, though not 

 actually a vital one, is however found only in 

 the animal tissues; it does not depend directly 

 upon life, but results merely from the texture 

 and organization of those particles which con- 

 stitute the vital organs. The following passage 

 from his work upon " Life and Death" may, 

 perhaps, assist us in understanding his views 

 upon this subject. " Most organs of our 

 bodies are held in a state of tension by various 

 causes ; the voluntary muscles by their anta- 

 gonists ; the hollow muscles by the substances 

 contained within them ; the vessels by means 

 of their circulating fluids; the skin of one 

 portion of the body by that which covers the 

 neighbouring part; the alveolar walls by the 

 teeth contained within them. Now, upon the 

 suspension of the distending causes, contrac- 

 tion takes place : divide a long muscle, its 

 antagonist becomes shortened; empty a hol- 

 low muscle, it shrinks upon itself: prevent the 

 blood from entering an artery, the vessel be- 

 comes a ligament: cut through the integu- 

 ments, the divided edges are separated from 

 each other by the contraction of the adjoining 

 skin : extract a tooth from its alveolus, that 

 channel becomes obliterated. * * * In all these 

 cases it is the removal of a tension naturally 

 inherent in the tissue which determines its 

 contraction : in other instances it is the re- 

 moval of a tension which does not naturally 

 reside in the part. Thus we see the abdomen 

 contract after parturition ; the maxillary sinus 

 after the extirpation of a fungous growth ; the 

 cellular tissue after the removal of an abscess ; 

 the tunica vaginal is after the operation for 

 hydrocele ; the integument of the scrotum 

 after the removal of an enlarged testicle ; the 

 aneurismal sac upon the emptying of its fluid." 

 He remarks in another place that motion 

 when the result of elasticity is quick and sud- 

 den, and ceases as abruptly as it has been pro- 

 duced; but the motions which result from 

 contractility of tissue are slow and impercep- 

 tible, lasting frequently for hours and even 

 days, as are seen in the retraction of muscles 

 after amputation. The distinction laid down 

 in these passages appears to us totally un- 

 supported : to say, for example, that even in a 

 dead artery there are two principles of con- 

 traction which, though their mode of action is 

 literally the same, should nevertheless be con- 

 sidered distinct and referred to different sources, 

 appears contrary to every rule of philosophic 

 reasoning. As to the distinction drawn from 

 the comparative quickness of these motions, 

 it is only necessary to say that upon this view 

 of the subject even the movement of the 

 watch-spring itself cannot be attributed to elas- 

 ticity. We must then conclude that there are 

 two and only two forces to which all the 

 various movements of Jiving bodies can be 

 referred ; the one a vital force regulated by its 

 own proper laws, the other a general physical 

 property, whose mode of action is essentially 

 the same in organized and unorganized bodies : 

 the phenomena above enumerated by Bichat 



