48 ANATOMY. 



tinctly granular, as if composed of fine particles, called sarcous elements 

 (from sarx, flesh), in or upon which are elongated bodies, or nuclei. 

 When treated with diluted acetic acid, the substance of the fibre be- 

 comes transparent and the nuclei very distinct (see the fibre to the 

 right). Nitric and chromic acids break them up into fusiform bodies, 

 called fibre-cells, as at b, each including one of the nuclei, but being 

 without a recognizable envelope or limiting membrane. In certain 

 parts, as in the spleen of animals, in medium-sized bloodvessels, and 

 in the skin, single fusiform fibre-cells exist ; but, in most places, these 

 are joined in an overlapping manner, to form the so-called plain mus- 

 cular fibres. In the coats of the alimentary canal and elsewhere, these 

 fibres form interlacing bands arranged in broad layers or tunics. Their 

 extremities are never attached to the bone, but pass into bundles of 

 fibrous connective tissue, and, in the gullet, have been seen to present 



Fig. 24. 



Fig. 24. a (The Author), portions of four plain or unstriped muscular fibres from the bladder ; that on the 

 right is rendered transparent, and its contained nuclei more evident, by being acted on by acetic acid. 

 Magnified 170 diameters, b (Kolliker), two plain muscular fibre-cells from the pig's gullet, treated with 

 nitric acid ; one long one from the human intestine, and one from the coats of the dog's spleen, not treated 

 with nitric acid. Magnified 200 diameters. 



microscopic tendinous intersections. In the windpipe, they terminate 

 in bundles of elastic tissue ; in the skin, often on the sides of the hair- 

 follicles. 



The striped or striated muscular fibres. Fig. 25, are far more elabor- 

 ately organized, presenting a much more definite and regular structure. 

 They are soft, compressed or prismatic in shape, and marked with 

 beautifully regular cross-lines or striae. Each fibre is inclosed in a 

 delicate glassy-looking structureless tube called the sarcolemma, as 

 shown in the ruptured fibre, b; upon, or within, the sarcolemma, 

 numerous nuclei containing one or more nucleoli are seen on the appli- 

 cation of acetic acid. The soft substance of the fibre, transparent, 

 and of a yellowish hue, consists of numerous fine threads called fibrillce 

 or filaments, a and c, which are themselves composed of rows of cohe- 

 rent quadrangular particles called sarcous elements. The existence 

 of the fibrillae gives rise to faint longitudinal lines in the fibres ; whilst 

 the equal size, the uniform arrangement, and the accurate adaptation 

 of the sarcous elements, which act peculiarly on transmitted light, pro- 

 duce the more evident transverse striae. Sometimes, even, as shown 



