226 



ANIMAL PHYSIOLOGY. 



[LESSON 67. 



FIG. 350. 



Muscular fibre cleaving 

 transversely. 



general appearance of the fibre will indicate a breaking up of the 

 entire structure into small dice, or square cells containing discs. 



997. It is always uncertain in which direction a muscle will pre- 

 fer to split whether in the direction of its longitudinal elements, 

 the fibrillse, or in the direction of the transverse lines the cells. 

 A representation of cleavage in the latter direc- 

 tion may be seen at Fig. 350. 



998. It has been remarked that the elements 

 of a muscle (fibres) are connected to each other 

 by areolar tissue; the elements of a fibre (ultimate 

 fibrillse) are similarly connected ; but a fibre is 

 enveloped in a distinct and characteristic tissue 

 the myolemma (sheath of the muscle), or 

 simple membrane in the animal kingdom. 



999. This sheath is quite distinct from areo- 

 lar, or any other tissue. Its existence can easily 

 be demonstrated in any muscular fibre by sub- 

 jecting it to the action of fluids, which occasion 



a swelling of its contents ; such is the effect of acids and alkalies, and 

 the result may be obtained by citric and tartaric acids, or by potash. 

 1000. There is no reason to believe that the myolemma is per- 

 forated, either by nerves or capillary blood-vessels ; it rather seems 



to present an impenetrable barrier 

 between the real elements of muscu- 

 lar structure and the surrounding 

 parts. 



1001. Muscular tissue, properly 

 so called, is extra (non) vascular ; for 

 its fibres are not penetrated by ves- 

 sels ; and the nutriment required for 

 its growth must be drawn by absorp- 

 tion through the myolemma. 



1002. Still, the substance of mus- 

 cle, as a whole, is remarkably vascu- 

 lar ; the capillary vessels being dis- 



a. Artery; 6, tributed in parallel lines, running in 

 the direction of the fibres, and united 

 by transverse branches in the minute interspaces between the fibres ; 

 so that, in all probability, there is no fibrilla which is not in close 

 relation to a capillary (Fig. 351). 



1003. The striped muscles, or muscles of animal life, as they 



FIG. 351. 



c, Capillaries. 



