PROPERTIES OF MUSCULAR TISSUE. 461 



The voluntary muscles are freely supplied with bloodves- 

 sels ; the capillaries form a network with oblong meshes around 

 the fibres on the outside of the sarcolemma. No vessels pene- 

 trate the sarcolemma to enter the interior of the fibre. 



Nerves also are supplied freely to muscles; the voluntary 

 muscles receiving chiefly nerves from the cerebro-spinal system, 

 and the unstriped muscles from the sympathetic or ganglionic 

 system. 



Properties of Muscular Tissue. 



The property of muscular tissue, by which its peculiar 

 functions are exercised, is its contractility, which, in the con- 

 traction or shortening of muscle, is excited by all kinds of 

 stimuli, applied either directly to the muscles, or indirectly to 

 them through the medium of their motor nerves. This prop- 

 erty, although commonly brought into action through the 

 nervous system, is inherent in the muscular tissue. For 1st, 

 it may be manifested in a muscle which is isolated from the 

 influence of the nervous system by division of the nerves sup- 

 plying it, so long as the natural tissue of the muscle is duly 

 nourished; and 2dly, it is manifest in a portion of muscular 

 fibre, in which, under the microscope, no nerve-fibre can be 

 traced. 



If the removal of nervous influence be long continued, as 

 by division of the nerve supplying a muscle, or in cases of paral- 

 ysis of long standing, the irritability, i. e., the power of both 

 perceiving and responding to a stimulus, may be lost ; but 

 probably this is chiefly due to the impaired nutrition of the 

 muscular tissue, which ensues through its inaction (J. Reid). 

 The irritability of muscles is also of course soon lost, unless a 

 supply of arterial blood to them is kept up. Thus, after liga- 

 ture of the main arterial trunk of a limb, the power of moving 

 the muscles is partially or wholly lost, until the collateral cir- 

 culation is established; and when, in animals, the abdominal 

 aorta is tied, the hind legs are rendered almost powerless (Se- 

 galas). So, also, it is to the imperfect supply of arterial blood 

 to tile muscular tissue of the heart, that the cessation of the 

 action of this organ in asphyxia is in some measure due (p. 

 189). ( 



Besides the property of contractility, the muscles, especially 

 the striated or those of animal life, possess sensibility by means 

 of the sensitive nerve-fibres distributed to them. The amount 

 of common sensibility in muscles is not great; for they may be 

 cut or pricked without giving rise to severe pain, at least in 

 their healthy condition. But they have a peculiar sensibility, 

 or at least a peculiar modification of common sensibility, which 



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