NON-STRIATED MUSCULAR TISSUE. 157 



or lines are also often apparent, but are less regular than the 

 strige. The component fibrillse of a muscular fibre may be demon- 

 strated by macerating the tissue in strong alcohol, and pressing 

 the prepared object, when each fibrilla will be seen to consist of 

 a row of alternately light and dark spots. By other means, such 

 as treatment with hydrochloric acid, or by a smart blow, a 

 muscular fibre may be separated into transverse discs correspond- 

 ing to its striated appearance. These two 

 separations of a fibre have been termed the 

 longitudinal and transverse cleavages. Could 

 both these operations be performed on the 

 same fibre, the result would be a crucial cleav- 

 age of it into a number of objects which would 

 appear under a high power as dark spots, with 

 light spaces round them, both being rectang- 

 ular in form ; they are known as the' sarcous 

 elements of Botvman, and in them rests the 

 inherent -power of contractility. Thus a trans- 

 verse row of sarcous elements forms a disc ; ' a 

 longitudinal row a fibrilla. When seen through 

 the medium of the sarcolemma the dark spots 

 appear transversely as a continuous line, hence 

 the striated appearance of the fibre. The fig. 68. 



fibres cleave more readily into fibrilte than striated muscular fibres 



. , T from the Horse. 



into discs. 



Modern observation modifies the above, the fibre being gener- 

 ally regarded as a series of alternate light and dark discs, the 

 latter having on each transverse surface a number of darker 

 granules, connected by fine longitudinal and transverse lines. 

 The former with their nodular extremities are termed muscle-rods. 

 A number of oval objects, related with the sarcolemma, appear 

 on treating a fibre with acetic acid ; these are the muscle 

 corpuscles, and they are nucleated. Striated fibres are for the 

 most part isolated, but those of the heart, which, as already 

 stated, are involuntary, divide into branches, and the branches 

 of different fibres frequently join, or, as it is termed, anastomose. 

 (Fig. 152.) 



NON-STRIATED MUSCULAR TISSUE. 



Involuntary or non-striated muscular tissue is pale in colour, 

 and consists of fibres, bound into fasciculi by a fine perimysium of 

 areolar tissue. 



The fibres never terminate in tendons, and are not invested in 

 a sarcolemma ; they are cylindrical in > shape, and composed of 



