STRUCTURE OF MUSCLE. 



437 



are arranged. Fig. 219 is from the human biceps, and Fig. 220 from 



Fig. 219. 



Fig. 220. 



Hansverse section of human muscle. 



Muscular fas- the pectoral 

 cicuii. muscle of the 



teal. Since it is in the 

 interspaces between the 

 rounded fasciculi that 



the blood-VeSSels lie, the Transverse section of muscle of teal. 



tissue is more vascular as its fasciculi are of less diameter. 



It has already been stated, in connection with Fig. 211, that the stri- 

 ated form of muscular fibre derived its name from the circumstance that, 

 when examined by a sufficiently high power, it appears to be crossed by 

 delicate transverse lines, the longitudinal separations between the fibrils 

 being also visible. This is seen in the specimen of insect muscle repre- 

 sented in the photograph, Fig. 221, and under a still higher magnifying 



Fig. 221. 



Fig. 222. 



Non-fibrillated insect fasciculi, magnified 50 diameters. 



power in that of Fig. 222. The dis- 

 tance between the transverse stria3 va- 

 ries with the condition of the muscle, 

 but on an average it is represented as N 0n -fibriiiated insect fasciculi, magnified 200 

 being about the ^ of an inch. Many 



more stria3 are crowded together when contraction takes place, and they 

 retire from each other as soon as relaxation occurs. 



It is said that the voluntary muscles contain in their muscle juice 

 more acid than is enough to neutralize all the alkali of the 



blood. The electro-chemical relations of this interfascicular 



Muscle juice. 



