372 



MUSCULAR MOTION. 



Loop-like termination of the Nerves 

 in voluntary muscle. After Burdach. 



(Todd and Bowman.) 



158< spinal marrow, forming part of a nerv- 



ous trunk ; turns around one or more, 

 muscular fibres, and returns along the 

 same or a neighbouring trunk to the 

 posterior column of the marrow. 



The red colour of muscles is usually 

 ascribed to the blood distributed to 

 them, as it may be removed by repeated 

 washing and maceration in water or 

 alcohol, without the texture of the mus- 

 cle being modified. By some, it has 

 been thought, that a quantity of red 

 blood remains attached to the fibres, 

 and is extravasated from the vessel : by 

 others, it is presumed with more proba- 

 bility to be contained in the vessels, and 

 according to Mulder, 1 who considers 

 the red colour to be wholly due to the 

 blood in the capillary system of the 

 muscles, when they are injected with 

 water, every muscle is colourless. Bi- 

 chat 2 conceived, that the colour is de- 

 pendent upon some foreign substance 

 combined with the fibre; and he grounded 

 his opinion upon the circumstance that, in the same animal, some of the 

 muscles are always much redder than others, and yet they do not appear 

 to have a greater quantity of blood sent to them ; and also, that in dif- 

 ferent classes of animals the colour of the muscles does not appear to 

 correspond with the quantity of red blood circulating through their 

 vessels. The fact, however, that when muscles have been long in a state 

 of inaction they become pale ; and that, on the other hand, the colour 

 becomes deeper when they are exercised, is additional evidence, that 

 their colour is dependent upon the blood they receive, which is found 

 to diminish or increase in quantity, according to the degree of inactivity 

 or exertion. 



Muscles differ, like the primary fibre, at their extremities and centre ; 

 the former being composed of condensed areolar membrane ; the latter 

 of the muscular or fibrous tissue. The centre of a muscle is usually 

 called its venter or belly ; and the areolar texture at the extremities is 

 variously termed; that from which it appears to arise being called the 

 head or origin; and that into which it is inserted the tail, termination 

 or insertion. These terms are not sufficiently discriminative. We shall 

 find, that a muscle is capable of acting in both directions ; so that the 

 head and the tail the origin and insertion may reciprocally change 

 places. In ordinary language, however, the extremity at which the 

 albugineous tissue (if we adopt Chaussier's nomenclature), assumes a 

 rounded form, so as to constitute a cord or tendon, is called the inser- 



1 The Chemistry of Vegetable and Animal Physiology, translated by Fromberg, &c., p. 

 589, Edinburgh and Lond., 1849. a Anat. General., ii. 327, Paris, 1818. 



