MUSCULAR FIBRE. 



695 



Fig. 325. — White fibrous tissue from the 

 sclerotic coat of the eye. 



all the fasciae. It is sparingly supplied with capillaries 

 and nerves : the former always run in the areolar tissue, 

 connecting the bundles of fibres together ; in the gene- 

 rality of the fibrous tissues, the capillaries are not well 

 seen, except in that of the dura mater and periosteum ; 

 in other parts it must be injected to show them. 



The yellow fibrous tissue 

 is highly elastic ; it consists 

 of bundles of fibres covered 

 with, and connected together 

 by, areolar tissue : the fibres 

 are of a yellow colour, some 

 round, others flattened ; 

 they are not always paral- 

 lel, but frequently bifurcate 

 and anastomose with neigh- 

 bouring fibres. It is always ^£5) 

 difficult to separate the fibres o^j^ 

 from each other ; and when 

 separated, the elasticity of 

 each individual fibre is shown 

 by its tendency to curl up at the end. The fibres in the 

 human subject vary in diameter from the 1-5, 000th to 

 1-1 0,000th of an inch. Acetic acid of ordinary strength 

 does not act on yellow fibrous tissue ; nor for a very 

 long time after maceration in water or spirit does its 

 elasticity diminish. Very long boiling extracts from it a 

 minute quantity of a substance nearly allied to gelatine ; 

 neither nuclei nor a trace of a cell can be seen in it after 

 the addition of acetic acid : both are readily seen when 

 white fibrous element is treated with this acid. 



Muscular Fibre. — There are three different kinds of 

 muscular fibre found in the animal body : 1st, in the 

 muscle of the skeleton ; 2d, in the muscle of the heart ; 

 and 3d, in the stomach, intestine, &c. The functions of 

 muscular fibre may be referred to two kinds — voluntary 

 and involuntary. The muscles endowed with voluntary 

 power are those of the skeleton ; the involuntary are those 

 of the heart, stomach, intestine, &c. 



Muscular fibre is held together by a very delicate tubular 

 sheath, nearly resembling simple structureless membrane. 



