92 GENERAL ANATOMY OF THE TISSUES. 



nitrogenous and nitrogenous products of the decomposition of 

 the muscular tissue. 



The transversely striated muscles are in a high degree 

 contractile, and are the chief instruments of the animal 

 motions. Their elements are developed hy the coalescence of 

 round or stellate cells, whose contents change into a homoge- 

 neous, semi-fluid substance, and then break up into fibrils. Once 

 formed, the muscular fibres grow by the elongation and thick- 

 ening of their elements, and in their complete condition they 

 enjoy a very energetic nutrition, which is especially manifested 

 by the multiform products of their decomposition, as well as by 

 the circumstance that their powers are exhausted in a short 

 time when the circulation is suspended. Wounds of the 

 muscles never heal by transversely striated muscular substance; 

 but an adventitious formation of this tissue appears to occur 

 sometimes, though rarely. 



Transversely striated muscular tissue is found in the fol- 

 lowing parts : 



1. In the muscles of the trunk and extremities ; of the globe 

 of the eye, and in all those of the ear. 



2. In the muscles of many organs ; as the larynx, pharynx, 

 tongue, and oesophagus (upper half), the end of the rectum 

 (sphincter externus, levator ani), the genital organs (bulbo-ischio- 

 cavernosus, urethralis transversus, transversi perinm, cremaster, 

 muscular fibres of the round ligaments of the uterus, in part. 



3. In certain parts of the vascular System, e. g. in the heart 

 and in the walls of the great veins which open into it. 



[The muscular fibres of animals are not all composed of 

 bundles of transversely striated fibrils, but present a series 

 of other forms, which may best be grouped in the following 

 manner : 



1. Muscular tubes, with homogeneous, semi-solid, not trans- 

 versely striated contents (most Molluscs, Worms, and Radiata). 



2. Muscular tubes with a membrane, a semi-fluid, homo- 

 geneous, cortical layer in contact with it, and a fluid or gra- 

 nular, frequently transversely striated or nucleated central sub- 

 stance. (Muscles of Petromyzon in part, certain muscles [of the 

 lateral line and of the spiracles] of the plagiostome and osseous 

 Fishes. Muscles of the Hirudinidce, Lumbricidte, of Paludina in 

 part, and of Carinaria) . 



