CHAP. VII.] MUSCULAR ACTION. 171 



but, as that ceased, the muscle would elongate under the weight, 

 and the limb would remain suspended simply by the tenacity of the 

 part. If, now, the muscle were stretched between the hands, we 

 should find it to possess some slight elasticity. The elasticity and 

 much of the tenacity of muscles are attributable to the sarcolemma, 

 and to the capillary and areolar tissues. It does not appear that 

 elasticity is in any degree a property of the sarcous elements, and 

 their tenacity must be comparatively slight : but it is the sarcous 

 tissue alone that possesses contractility. 



Although it is universally allowed that the muscular tissue is the 

 contractile substance, yet the strange question has been raised, and 

 is still warmly debated, whether it possesses this power in itself, 

 and independently of all other tissues: some contending that 

 nerve is necessary to confer contractility on muscle, to charge it, as 

 it were, with this property j others, that nerve is only necessary to 

 call it into action ; and others, that the property is the essential 

 attribute of the tissue, and totally independent of all nerves. The 

 time is past when the intricacies of this keen contest can be 

 threaded with any benefit to the student, and we therefore refrain 

 from attempting to follow them. We shall prefer offering him a 

 view of the facts of the subject, as at present known, drawing 

 our conclusions as they arise. 



The contractility of muscle is exhibited in two varieties of con- 

 traction, passive and active. 



Passive Contraction is that which every muscle is continually 

 prone to undergo, by the mere quality of its tissue, as long as it 

 remains in its natural situation in the body. The muscles are ever 

 kept on the stretch by the nature of their position and attachments, 

 and cannot have their ends so approximated, by attitude or other- 

 wise, as that their tendency to shorten themselves shall cease. If, 

 for example, the rectus muscle of the thigh have its extremities 

 brought as near together as can be effected artificially by posture, 

 they would yet be found to approach still nearer on being freed 

 from their attachment to the bones. The stimulus to this contrac- 

 tion may be therefore considered to be that of extension. In frac- 

 tures and dislocations attended with shortening of the limb, the 

 muscles adapt themselves permanently to their shortened state by 

 virtue of this property. This tendency to contract has been dis- 

 tinguished by the term retractility, from its being manifested by the 

 retraction that occurs when the belly of a muscle is cut across. 

 But, in this instance, the retraction would appear to be in part 



