THE MUSCLES AND NERVES. 285 



such united muscle segments, an idea first suggested by 

 Jaworowski.* 



The Ultimate Structure of all these forms of muscle exhibits a 

 perfect uniformity of type. It is not my intention to give even 

 a resume of the very various accounts of the minute structure of 

 muscle which are still under discussion. For details on this 

 subject the reader may refer to the tenth edition of Quain's 

 ' Elements of Anatomy,' in which he will find a good biblio- 

 graphy of the recent literature on the subject. The only memoir 

 which agrees with my own observations is by Biitschli and 

 Schewiakoff [134], and their results so completely accord with 

 my own, that I shall give a resiuiu' of them. 



According to these authors, each fibre, muscle cell, or bundle; 

 of primitive fibrillse, consists of two varieties of protoplasm — a 

 contractile fibrillar substance and ordinary protoplasm, inter- 

 mediate substance. The contractile fibrils, or primitive fibrillce, 

 are fine fibres with their long axes parallel to the long axis of 

 the fibre. In transverse sections they appear prismatic, highly 

 refractive dots, surrounded by the less refractive protoplasm, 

 the intermediate substance or sarcoglia of Kiihne. The trans- 

 verse sections of the fibrilla; give rise to the appearance known 

 as ' fields of Cohnheim.' The intermediate substance, sarcoglia 

 or sarcoplasm, is distinctly reticular, but the reticulation is 

 very irregular. The muscle nuclei are imbedded in this sub- 

 stance. The saixolemma may be either a distinct membrane, 

 as in the larval muscles, or merely a more or less condensed 

 layer of reticular sarcoplasmic fibres. 



Each contractile fibril is formed of two kinds of material, one 

 anisotropous, the other isotropous. The anisotropous sub- 

 stance consists of prismatic or strap-shaped segments ; these 

 are united in a linear series by the isotropous substance, which 

 they regard as a cement material. 



The authors quoted state that the primitive fibril, contractile 



substance, is also reticular. Their figures are, however, more 



readily understood than their description, and it appears that 



the prisms of anisotropous substance are formed by still 



* Siizungbericht, K., Acad. Wien, Bd. Ixxx., 1879. 



