204 



VETERINARY PHYSIOLOGY 



across the cell.,. Lastly, a covering, the sarcolemma, is 

 formed. The fully-formed fibre thus consists of three 

 parts. 



(1) The Sarcolemma is a delicate, tough, elastic mem- 

 brane closely investing the 

 fibre, and attached to it at 

 Dobie's lines. 



(2) The Muscle corpuscles 

 consist of little masses of 

 protoplasm each with a 

 nucleus, which lie just under 

 the sarcolemma. 



(3) The Sarcous substance 

 is made up of a series of longi- 

 tudinal fibrils, each made up 

 of alternate dion and clear 

 bands embedded in the pro- 

 toplasm or sarcoplasm, as it 

 is generally called. The dim 

 bands stain deeply with eosin 

 (fig. 101). In the middle of 

 the clear band is a narrow 

 dark line, Dobie's line. The 

 fibres and fibrils tend to 

 break across in the region 

 of the clear band, showing 

 that they are weakest at 

 that part. The clear band 

 differs from the dim band, 

 not only in not laking up 

 eosin, but also in the fact 



Fig. 10.3. — To show the nerves con- 

 nected with skeletal muscle. 3, 

 The ingoing proprioceptive fibres ; 

 e, the nerve cells of the anterior 

 horn, from which spring the true 

 somatic fibres which have been cut 

 in the anterior root ; the degen- 

 erated part is shown in the dotted 

 line ; 1, the fibres of the sympath- 

 etic system with their cell stations 

 in the sjmipathetic ganglion. The 

 post-ganglionic part is not degen- 

 erated, and its endings persist in 

 the muscle, as shown in fig. 105. 

 (Barenxe.) 



that it entirely prevents the 

 passage of polarised light except in one position of the 

 analysing prism, while the dim band allows polarised 

 light to pass, whatever be the position of the prism. 

 The fibrils of a muscle fibre must be considered as 

 a distinct development of the sarcoplasm in which 

 they lie embedded. They have been called sarcostyles. 

 Various explanations of the cross striping have been given. 



