68 GENERAL ANATOMY. 



found only in the perimysium, between the muscular fasciculi. The smaller ves- 

 sels present peculiar saccular dilatations, which are supposed to act as receptacles 



for the blood during the contraction of the muscular 

 fibres, when it is pressed out from some of the capil- 

 laries. 



Nerves are profusely distributed to striped 

 muscle. The mode of their termination will be 

 described on a subsequent page. 



The existence of lymphatic vessels in striped 

 muscle has not been ascertained, though they have 

 been found in tendons and in the sheath of the 

 muscle. 



The unstriped muscle, or muscle of organic life, is 

 found in the walls of the hollow viscera viz. the 

 lower half of the oesophagus and the whole of the 

 remainder of the gastro-intestinal tube ; in the trachea 

 an d bronchi, and the alveoli and infundibula of the 

 lungs ; in the gall-bladder and ductus communis 



- muscular chofedochus ; in the large ducts of the salivary and 



fibres of the heart seen in a longitu- pancreatic glands; in the pelvis and calices of the 



dinal section. On the right the lira- f., , c 1111 i ,1 i 



its of the separate cells with their kidney, the ureter, bladder, and urethra ; m the 

 gr u a c mmat r fca e iiy hibil female sexual organs viz. the ovary, the Fallopian 



tubes, the uterus (enormously developed in preg- 

 nancy), the vagina, the broad ligaments, and the erectile tissue of the clitoris ; in 

 the male sexual organs viz. the dartos scroti, the vas deferens and epididymis, 

 the vesiculae serninales, the prostate gland, and the corpora cavernosa and corpus 

 spongiosum ; in the ducts of certain glands, as in Wharton's duct; in the capsule 

 and trabeculge of the spleen ; in the mucous membranes, forming the muscularis 

 mucosge ; in the skin, forming the arrectores pilorum, and also in the sweat- 

 glands ; in the arteries, veins, and lymphatics ; in the iris and the ciliary muscle. 



Plain or unstriped muscular fibre is made up of spindle-shaped cells, called 

 contractile fibre-cells, collected into bundles and held together by a cement-sub- 

 stance, in which are contained some connective-tissue corpuscles (Fig. 43). These 

 bundles are further aggregated into larger bundles or flattened bands, and bound 

 together by ordinary connective tissue. 



The contractile fibre-cells (Fig. 44) are elongated, spindle-shaped, nucleated 

 cells of various lengths, averaging from -$^-$ to -3-^5- of an inch in length, and ^3^0" 

 to "s^Vo of an inch in breadth. On transverse section they are more or less poly- 

 hedral in shape, from mutual pressure. They present a faintly longitudinal stri- 

 ated appearance, and consist of an elastic cell-wall containing a central bundle of 

 fibrillge, representing the contractile substance, and an oval or rod-like nucleus, 

 which includes, Avithin a membrane, a fine network communicating at the poles 

 of the nucleus with the contractile fibres (Klein). The adhesive interstitial sub- 

 stance, which connects the fibre-cells together, represents the endomysium, or del- 

 icate connective tissue which binds the fibres of striped muscular tissue into fas- 

 ciculi ; while the tissue connecting the individual bundles together represents the 

 perimysium. The unstriped muscle, as a rule, is not under the control of the will, 

 nor is the contraction rapid and involving the whole muscle, as is the case with the 

 muscles of animal life. The membranes which are composed of the unstriped 

 muscle slowly contract in a part of their extent, generally under the influence of 

 a mechanical stimulus, as that of distension or of cold ; and then the contracted 

 part slowly relaxes while another portion of the membrane takes up the contrac- 

 tion. This peculiarity of action is most strongly marked in the intestines, con- 

 stituting their vermicular motion. 



Chemical Composition of Muscle. In chemical composition the muscular fibres 

 of both forms consist mainly of a proteid substance myosin which is classed 

 as one of the globulins. It is readily converted by the action of dilute acids 



