MUSCLES. 473 



containing a greater number of fleshy fibres, in proportion to the 

 tendinous, than those of the adult." 



" They are in general divided into hollow and solid. The first, 

 not directly subject to the will, belong more to the vital and 

 natural functions." They are the heart, one of the coats of the 

 alimentary and respiratory canals, of the urinary bladder, and 

 of some blood-vessels j and are seen in a few other parts. They 

 shorten and narrow the cavity or canal which they surround. 



" Among the second," which are subject to the will, " there is 

 much variety. For, not to allude to difference of size, there is 

 great diversity in the disposition of their bands and fasciculi, the 

 direction of their fibres, the proportion of the fleshy to the 

 tendinous part, their course, mode of insertion, &c. 



" The greatest number are long, and their fleshy bellies," lying 

 outside solid parts, and passing over one or more joints, "terminate 

 at each extremity in tendinous chords, inert, and destitute o 

 contractility, and fixed to different bones, which, while con- 

 tracting, they move in the manner of levers." The movable 

 solids are drawn towards each other, if of equal mobility and 

 size; if not, that which is movable or more movable and small is 

 drawn towards the other. 



" The commonly received law that a muscle during its con- 

 traction draws the more movable point of insertion to the more 

 fixed, must be considered, as Winslow justly remarks k , perfectly 

 relative and subject to various limitations. Thus, for example, 

 sometimes the one point, and sometimes the other, may be the 

 more movable, accordingly as the united action of many different 

 muscles may render the opposite more fixed." 



" While a very few muscles are destitute of tendons, such as the 

 latissimus colli, an equally small number are not inserted into 

 bones," but into soft solids, as into the lips, palate, tongue, 

 pharynx, nose, eye, ears, genitals. These approach the hard part 

 during contraction. 



" A property common to all muscles is to become shorter, more 

 rigid, and generally unequal, and, as it were, angular, during 

 contraction," gaining in thickness what they lose in length. 

 Dr. Tiedemann argues that, in contracting, a muscle acquires 

 greater density, because it will support or raise a weight which 

 would tear it after death. This, however, shows only the more 



k Mem. de VAcad. des Sc, de Paris. 1720." 



