54 



GENERAL ANATOMY. 



fibres are attached to the skin or mucous membranes, the fibres are described 

 by Salter as becoming continuous with those of the areolar tissue. 



The primitive fasciculi consist of a number of filaments, inclosed in a tubular 



sheath of transparent, elastic, and apparently homo- 

 geneous membrane, named by Bowman the "sar- 

 colemma." The primitive fasciculi are cylindriform 

 or prismatic. Their breadth varies in man from 

 ?n?i to slU f an m ch, the average of the majority 

 ^eing about 7^; their length is not always in 

 proportion to the length of the muscle, but depends 

 on the arrangement of the tendons. This form of 

 muscular fibre is especially characterized by being 

 apparently marked with very fine, dark lines or 

 strise, which pass transversely round the fibre, in 

 curved or wavy parallel directions, from y^^tr to 

 T-jffun f an i ncn apart. Other stria? pass longitu- 

 dinally over the fibres, indicating the direction of 

 the primitive fibrils of which the primitive fasci- 

 culus is composed. They are less distinct than the 

 former. 



The primitive fibrils constitute the proper con- 

 tractile tissue of the muscle. Each fibril is cylin- 

 driform, somewhat flattened, about jgJnTj an i ncn 

 in thickness, and marked by transverse stria? placed at the same distance from 

 each other as the stria? on the surface of the fasciculus. Each fibril apparently 

 consists of a single row of minute particles (named " sarcous elements" by 



Transverse section from the ster- 

 no-mastoid in man (50 times mag- 

 nified), a. External perimysium. 

 b. Internal perimysium. e. Primi- 

 tive and secondary fasciculi. 



Fig. 22. 



e c" 



Two human muscular fibres 

 (magnified 350 times). In the 

 one, the bundle of fibrillse 

 (b) is torn, and the sarco- 

 lemraa (a) is seen as an empty 

 tube. 



Fragments of striped elementary fibres, showing a cleavage in op- 

 posite directions (magnified 300 diameters). A. Longitudinal cleavage. 

 The longitudinal and transverse lines are both seen. Some longitudinal 

 lines are darker and wider than the rest, and are not continuous from 

 end to end. This results from partial separation of the fibrillae. 

 c. Fibrillae separated from one another by violence at the broken end 

 of the fibre, and marked by transverse lines equal in width to those 

 on the fibre, c' c" represent two appearances commonly presented 

 by the separated single fibrillae (more highly magnified). At c' the 

 borders and transverse lines are all perfectly rectilinear, and the in- 

 cluded spaces perfectly rectangular. At c" the borders are scalloped, 

 and the spaces bead-like. When most distinct and definite, the fibrilla 

 presents the former of these appearances. B. Transverse cleavage. 

 The longitudinal lines are scarcely visible, a. Incomplete fracture 

 following the opposite surfaces of a disk, which stretches across the in- 

 terval, and retains the two fragments in connection. The edge and 

 surfaces of this disk are seen to be minutely granular, the granules 

 corresponding in size to the thickness of the disk, and to the distance 

 between the faint longitudinal lines, b. Another disk nearly detached. 

 b> '. Detached disk, more highly magnified, showing the sarcous elements. 



