MUSCULAR FIBRE. 613 



the most part about 1-1 0,000th of an inch. It has been observed, 

 however, as high as l-5000th of an inch, and as low as l-20,000th, 

 even when the fibre was not put upon the stretch. 



427. The "smooth" or non-striated form of Muscular fibre, 

 which is especially found in the walls of the stomach, intestines, 

 bladder, and other similar parts, is composed of flattened bands 

 whose diameter is usually between 2-2000th and l-3000th of an 

 inch; and these bands are collected into fasciculi, which do not 

 lie parallel with each other, but which cross and interlace. By 

 macerating a portion of such muscular substance, however, in 

 dilute nitric acid (about one part of ordinary acid to three parts 

 of water) for two or three days, it is found that the bands just 

 mentioned may be easily separated into elongated fusiform cells, 

 not unlike woody fibre in shape; each distinguished for the most 

 part by the presence of a long staff-shaped nucleus, brought into 

 view by the action of acetic acid. These cells, in which the dis- 

 tinction between cell-wall and cell-contents can by no means be 

 clearly seen, are composed of a soft yellow substance, often con- 

 taining small pale granules, and sometimes yellow globules of 

 fatty matter. In the coats of the bloodvessels are found cells 

 having the same general characters, but shorter and wider in 

 form ; and although some of these approach very closely in their 

 general appearance to epithelium-cells, yet they seem to have 

 quite a different nature, being distinguished by their contractile 

 endowments. 



428. In the examination of Muscular Tissue, a small portion 

 may be cut out with the curved scissors; and this should be torn 

 up into its component fibres, and these, if possible, should be 

 separated into their fibrillre, by dissection with a pair of needles, 

 under the simple microscope. The general character of the 

 striated fibre are admirably shown in the large fibres of the 

 Frog; and by selecting a portion in which these fibres spread 

 themselves out to unite with an aponeurotic expansion, they 

 may often be found so well displayed in a single layer, as not 

 only to exhibit all their characters without any dissection, but 

 also to show their mode of connection with the simple fibrous 

 tissue of which the aponeurosis is formed. As the ordinary cha- 

 racters of the fibre are but little altered by boiling, this process 

 may be had recourse to for their more ready separation, espe- 

 cially in the case of the tongue. The separation of the fibres 

 into their fibrillse is only likely to be accomplished, in the higher 

 Vertebrata, by repeated attempts, of which the greater number 

 are likely to be unsuccessful ; but it may be accomplished with 

 much greater facility in the Eel and other fish, the tenacity of 

 whose muscular tissue is much less. The characters of the 

 fibrillse are not nearly so well pronounced, however, in the Fish, 

 as in the warm-blooded Vertebrata; and among the latter, the 

 Pig has been found by Mr. Lealand (who has been peculiarly 

 successful in this class of preparations) to yield the best examples. 



