MUSCULAR TISSUE OF THE HEART. 



119 



It is generally collected into larger and smaller fasciculi, which in many- 

 cases cross one another and interlace. The fasciculi are connected at 

 their ends with tendinous tissue, and are thus inserted into the mem- 

 branous and firmer parts in the neighbourhood. Small tendons are 

 also fixed by blending with the fibrous sheaths investing contiguous 

 muscular bundles. Ellis states that in the gullet the longitudinal mus- 

 cular fasciculi are intersected wholly or partially, at intervals of from -t\^ 

 to yV ^^ ^^^ inch, by small tendons into which they are inserted, after 

 the fashion of the rectus abdominis, only on a miniature scale. 



The plain muscular tissue is met with in the lower half of the gullet, 

 the stomach, and the whole intestinal canal ; that is, both in the 

 muscular coat of the alimentary canal, and also as a layer in the tissue 

 of the mucous membrane, and in the villi ; in the trachea and bronchial 

 tubes, in the bladder and ureters, and the ducts of the larger glands 

 generally, in the uterus and its appendages, in the corpora cavernosa of 

 both sexes, in the prostate gland, and in the ciliary muscle and iris. 

 The middle coat of the arteries, the coats of many veins and the larger 

 lymphatics contain plain muscular tissue. It has also been detected in 

 certain parts of the skin, in the dartos or subcutaneous tissue of the 

 scrotum, and in form of minute muscles attached to the hair-follicles. 



Muscular Tissue of the Heart. — The fibres of the heart differ 

 remarkably from tliose of involuntary muscular organs in general, in- 

 asmuch as they present transverse stria?. The striae, however, are less 

 strongly marked, and less regular, and the fibres are smaller in dia- 

 meter than in the voluntary muscles. They differ also from these in 

 being made up of distinct quadrangular cells (fig. 78) joined end to 



Fig. 78. 



Fig. 79. 



Fig. 78. — Six IMusculak Fibke-Cells from the Heart. Magnified 425 Diameters. 



a, line of junction between two cells ; b, c, branching of cells. 

 From a drawing by Mr. J. E. Neale. 



Fig. 79. — Muscular Fibres from the Heart, magnified, showing their cross 

 STRij;, divisions, and junctions (KiJlliker. ) 



end and often presenting a branched or forked appearance near one 

 extremity (c.) Each cell has commonly a single clear oval nucleus 



