58 



ELASTICITY. 



are certainly not the result of vital action (for 

 he admits tliiit the contractility of tissue to 

 which he ascribes them is not destroyed by 

 death) : they must then be owing to a physical 

 force, and amongst the various physical agen- 

 cies we are acquainted with, elasticity is the 

 only one to which they can be referred. 



The " vis mortua" of Haller appears like- 

 wise to differ little if at all from elasticity. 

 Speaking of this force he observes, that, as 

 indeed the very name implies, it is totally in- 

 dependent of life, and adds " Haec vis in 

 partibus animalium perpetuo agere videtur, 

 etiamsi non perpetuus effectus adparet. Vi- 

 detur enim contractio cuique particulse propriae 

 a contraria contractione duorum elementorum 

 vicinorum impugnari et distrahi, ut quae 

 breviores fieri non possunt, quin mediam par- 

 ticulam distrahant. Id dum fit in omnibus, 

 quies videtur, qua; est summa virium contra- 

 riarum se destruentium. Quam primum vero 

 aliqua particula a sodalibus separatur, inflicto 

 vulnere, tune utique labium vulneris, nunc 

 liberum, nee a conlraria potestate retentum, se 

 ad earn vicinam, a qua trahitur, integramque 

 incise membranae partem retrahit." The facts 

 so accurately described in this passage are 

 easily explained by the operation of elasticity. 

 Why then multiply causes ? Why assume the 

 existence of another principle in order to ac- 

 count for them ? The phenomena ascribed by 

 Cullen and others to what he terms " ttmiciti,," 

 are also, at least in many instances, the effects 

 of the same physical force. (See CONTRAC- 

 TILITY.) 



II. The tissues of the animal body are pos- 

 sessed of very various degrees of elasticity; 

 some of them are but little inferior to the most 

 highly elastic unorganized substances, while 

 others are endowed with this property in so 

 very trifling a degree, that in our physiological 

 and pathological reasonings concerning them, 

 we may almost consider it as absent. We 

 shall endeavour to arrange the principal organic 

 tissues in the order of their elasticity, and shall 

 then proceed to offer a few remarks upon each. 



1. Yellow fibrous tissue. 2. Cartilage. 3. 

 Fibro-cartilage. 4. Skin. 5. Cellular mem- 

 brane. 6. Muscle. 7. Bone. 8. Mucous 

 membrane. 9. Serous membrane. 10. Ner- 

 vous mutter. 11. Fibrous membrane. 



This view of the comparative elasticity of 

 the different tissues must not be regarded as 

 rigorously exact : owing to the impossibility 

 of procuring each one perfectly separate from 

 the others, the result of our experiments can be 

 considered merely as approximate. 



1. The yellow fibrous system. The tissues 

 composing this system are unquestionably the 

 most highly elastic of all : the ligamenta sub- 

 flava which unite the laminae of the vertebrae 

 to one another, and the ligamentum nuchae 

 which suspends the head in some of the larger 

 quadrupeds, are scarcely inferior to caoutchouc 

 in this respect. The middle coat of arteries 

 is referred by Beclard to the yellow fibrous 

 system, perhaps from its possessing in so high 

 a degree this characteristic property. Its exis- 



tence may be demonstrated by various experi- 

 ments, and many of the physiological and 

 pathological phenomena of the arterial tissue 

 are modified or determined by its presence. 

 The sudden expansion of an artery whether in 

 the living or dead body upon the removal of 

 a force pressing its sides together ; the gradual 

 contraction of a divided artery, by means of 

 which hemorrhage is so frequently arrested ; 

 the contraction or obliteration of the vessel 

 beyond the ligature, after it has been taken up 

 in aneurism ; the obliteration of the umbilical 

 arteries and of the ductus arteriosus soon after 

 birth ; the gaping which occurs in longitudinal 

 wounds of arteries owing to the recession of 

 the divided edges; the power possessed by these 

 vessels of accommodating their size to the 

 quantity of circulating blood, (thus causing 

 endless variations in the volume of the pulse 

 even in the same individual) ; all these facts 

 have been accounted for by the transverse 

 elasticity of the middle coat. The effects of 

 this property in a longitudinal direction may 

 be seen in the retraction of divided arteries 

 during amputation ; in the sort of locomotion 

 which these vessels undergo from the impulse 

 of the blood, and in the enlargement of a 

 transverse arterial wound by the retraction of 

 its edges. The proper coat of veins, though 

 belonging likewise to this system, is however 

 much less elastic than that of the arteries ; but 

 we cannot agree with those who deny this 

 property to the venous tissue. The sudden 

 flow of blood from a portion of vein included 

 between two ligatures ; the constantly varying 

 size of the cutaneous veins according to the 

 volume of their contents; the obliteration 

 under certain circumstances of veins where 

 circulation has been arrested, appear to us 

 explicable only by attributing this property to 

 them. 



2. Cartilage is possessed of very great elas- 

 ticity. On pressing the point of a scalpel 

 into cartilage it is expelled upon the suspension 

 of the force by the contraction of the sur- 

 rounding substance. It may also be well de- 

 monstrated by twisting or bending the carti- 

 lages of the ribs, or those of the nose, eyelid, 

 &LC. The elasticity of cartilage in the adult is 

 much greater than in the child or old person. 

 We shall allude presently to the several impor- 

 tant objects to which this property as connected 

 with cartilage is applied. 



3. Fibru-cartiliige. The elasticity of this 

 tissue may be studied in the intervertebral 

 fibre-cartilages, in which it contributes so 

 remarkably to the obscure movements of the 

 spinal column and to the security of the chord : 

 it is remarkably displayed in restoring the sub- 

 stance to its proper condition, when pressure 

 rather than twisting or bending has been the 

 cause of derangement. The fibro-cartilaginous 

 funnels through which the tendons are trans- 

 mitted, possess likewise this property to a great 

 extent. Bichat found, on removing a tendon 

 in a living dog, that the funnel through which 

 it had been transmitted became impervious, 

 like an artery under similar circumstances. 



