Hi PHYSIOLOGY OF MUSCLES AND NERVES, 



cadi flier. Briicke, therefore, supposes that tin- muscle 



substance i- in itself homogeneous or uniform, luil that 

 iu it a iv in-erted small particles \vliich are <>(' double- 



refracting power. When these particles are massed in 

 lar^e numbers, and arc regularly arranged, they refract 

 the linT.t doubly, so that the whole of that particular 

 part seems to refract doubly, while the inieriuediate 

 parts, since they contain few or none of the particles 

 in question, continue i refract simply. Tlie-e latter 

 parts, however, when seen under ordinary un polarised 

 light, so that it is impossible to judge of their powers 

 of double refraction, appear lighter, Avhile the former 

 appear darker ; and so toget her they cause the striated 

 appearance of the nuix-le. 



3. In one of these muscle-fibres it is ne.v.-sary (,, 

 di-tiiiinil>h the contained matter and the containing 

 pouch. The latter is called the muscle-fibre pouch, or 

 MI fi;>ti ,,uiia. In it, especially after the addition of 

 aci-tic arid, \\hich causes the whole fibre to swell ;:nd 

 become more transparent, a number of longish pointed 

 kernels (nuclei) are seen, and similar kernels occur also 

 in parts within the muscle-fibre. To the ends of the 

 muscle-fibre, which are rounded and are very uniformly 

 enclosed by the pouch, which must therefore be re- 

 garded as a lon^r closed sac, the white cords mentioned 

 ;;lio\e attach themselves, and these are completely 

 coalescent with the sarcolemma. 



They consist of strong slender threads of the naf lire 

 of the so-called connective fi>Hie. As a considerable 

 number of muscle- fibres constitute the trunk of the 



muscle, these threads also unite into cords which are 



called the miix-le-teiidons. They are sometimes ,-hort . 

 sometime- loiiL, r , thicker or thinner according to the 



