CHAP, v.] 



THE CAT'S MUSCLES. 



125 



its substance of water, while about fifteen per cent, of the remaining 

 fourth is found, after death, to consist of an albuminoid substance 

 called syntonin, or muscle fibrin, *' which is soluble in dilute hydro- 

 chloric acid. It seems, however, that this post-mortem condition 

 differs from what is found in life, when the muscle-fibrin is fluid, 

 and has been termed myosi)i. Muscle-fibrin contains some fifteen 

 per cent, of nitrogen. Other nitrogenous substances termed kreatin 

 and l-yoatiniue, are present in very small quantities, as also some 

 non-nitrogenous ones, such as grape-sugar, lactic, butyric, acetic, 

 formic, and uric acids, with some other substances. 



Muscular tissue is of two kinds, called respectively striped and 

 UNSTRiPED. The unstriped tissue takes part in the formation of the 

 alimentary canal and other viscera, such as the bladder. It also 

 exists in the walls of the blood-vessels, and generally in parts the 

 actions of which, in man, are not under the control of the will 

 Striped muscular tissue, on the contrary, makes up the substance of 

 all those muscles which answer to such as in us are amenable to the 

 will, together with some parts which act involuntarily — as the heart. 

 This striped kind is the more complex in structure. 



IJnstriped muscular tissue, as the more simple, may be first 

 noticed. It is pale, translucent, and made up of a number of roundish 

 or flattened fibres from the -j-TrVu- ^o the y^Vo- of an inch in breadth, 

 devoid of any limiting membrane, more or less fusiform in shape, 

 and marked at intervals with oblong corpuscles. Each fibre is made 

 up of bodies termed mmcuJar fibre cells, of an oblong, flattened 

 shape, of a granular substance, and containing an oval or rod-shaped 

 nucleus. The nuclei become very distinct when the fibres are treated 

 with dilute acetic acid. As well as forming fibres, those cells may 

 be mixed up with other tissues, as, e. g., in the dermis (where some 

 of them, by their contraction, may make hairs " stand on end" in 

 the way before spoken of), or they may form broad layers of inter- 

 lacing fibre-cells. They are never attached to bones. Sometimes 

 they bifurcate at one end. 



Striped muscular tissue consists of fibres which are generally 

 collected in larger or smaller bundles termed fasciculi (Fig. 76, A), 

 each fasciculus being furnished by a membranous envelope sent in- 

 wards from the sheath, or periniysium, which invests the whole 

 muscle, except in the heart, where the fibres are naked. Each 

 fibre (B) has a membranous transparent investment called the 

 sarcoloiuna (Fig. 7G, B e), which is of the nature of elastic tissue. 

 The fibres average about -^l-^ of an inch, but may be somewhat 

 larger or much smaller. 



Within the wall of the sarcolemma, there may be at intervals elon- 

 gated corpuscles, but the special characteristic of fibres of this tissue is 



* Fibrin is the name given to the soft, 

 whitish, stringy substance, which maybe 

 obtained from fresh blood by whipping 

 it with fine rods. It is vqry like albu- 



men, but differs by its property of spon- 

 taneous co-agulation. See the description 

 of the blood, Chapter VII., § 2. 



