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On the Histology of the Muscles of the Fly and their 

 Relation to the Muscles of Vertebrates. 



13y B. Thompson Lowne, F.R.C.S., Lecturer on Physiology in the 

 Middlesex Hospital Medical School, &c. 



(Read November 2Uh, 1887.) 



Our knowledge of the comparative histology of muscles has been 

 much retarded by the fact that authors have been slow to recognize 

 that the striated muscles of different forms of animal differ greatly 

 from each other. Thus the blow-fly exhibits three distinct types of 

 striated muscle, two of which differ materially from the ordinary 

 striated muscles of the mammalia. 



In mammals three forms of muscles are well known, non-striated 

 muscle, heart muscle, and striated muscle. With the first of these 

 the present paper is not concerned ; the two last exhibit transverse 

 striation. In heart muscle, the nuclei are situated in the centre of 

 the fibre, and there is no investing sheath or sarcolemma, whilst in 

 the skeletal muscles there is a distinct elastic investing sheath to 

 each fibre, and the nuclei are placed immediately beneath it. 



A transverse section of such a skeletal muscle fibre shows that it 

 consists of a number of prismatic columns, surrounded by an inter- 

 columnar substance ; thus the section is mapped out into irregular 

 fields, fields of Cohnheim.* The transverse sections of the columns 

 when highly magnified appear dotted with minute highly refractive 

 points. This appearance has been differently interpreted by 

 different observers; Schwann *f demonstrated the existence of 

 moniliform fibrillae, and I am inclined to regard these bright points 

 as the sections of the ultimate moniliform fibrillae of Schwann. 

 The moniliform fibrillar are cemented together into prismatic rods 

 or fibrils by an interfibrillar cement material ; the fibrillae are the 

 muscle rods of authors, and form the principal or contractile sub- 

 stance, whilst the cementing medium is the intermediate sub- 

 stance (Zwisehen-substanz) of Rollett. \ The columns of 

 united moniliform fibrillae are the " colonnettes " of Viallaines,§ 



* Virchow'a Archiv., Bd.34. f Strieker, " Comp. Histology," Vol. iii. 



X Strieker, I.e. § " Ann. Sc. Nat. Zool.," Gth ser., Tom. 14. 



