66 



GENERAL ANATOMY. 



bands, is resolved into the appearance shown in Fig. 40, which shows a series of 

 broad dark bands, separated by a light band, which is itself divided into two by a 

 dark streak. This streak is termed Krause' s membrane ; it is continuous at each 

 end with the sarcolemma investing the muscular fibre. Thus it may be said that 

 the fibre is divided into a number of transverse compartments by this membrane, 

 each compartment containing in the centre a dark plate with a bright border 

 above and below ; that is to say, between the dark central part and the membrane 

 of Krause. A muscular fibre presents, then, the appearance of the following 

 layers in regular alternation : a dark layer, the transverse disk ; a bright trans- 

 parent layer, the lateral disk ; a dark line, the intermediate disk or membrane of 

 Krause ; then another lateral disk, a transverse disk, and so on (Figs. 40 and 41). 

 This appearance, following the observations of Rollett, is due to the mode of for- 



FIG. 38. Two human muscular fibres. 

 Magnified 350 times. In the one, the bundle of 

 flbnllse (6) is torn, and the sarcolemma (a) is 

 seen as an empty tube. 



FIG. 39. Fragments of striped elementary fibres, 

 showing a cleavage in opposite directions. Magnified 

 300 diameters. A. Longitudinal cleavage. The longi- 

 tudinal and transverse lines are both seen. Soma lon- 

 gitudinal lines are darker and wider than the rest, and 

 are not continuous from end to end. This results from 

 partial separation of the fibrillse. c. Fibrillse 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 com- 

 monly presented by the separated single fibrillse (more 

 highly magnified). ' At c' the borders and transverse lines 

 are all perfectly rectilinear, and the included spaces per- 

 fectly 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 

 interval, 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. 6. Another disk nearly- 

 detached. 6'. Detached disk, more highly magnified, 

 showing the sarcous elements. 



mation of a muscular fibre, which is made up of two principal parts : 1, fibrillge ; 

 and 2, a hyaline or faintly granular substance, resembling protoplasm, and called 

 sarcoplasm. The fibrillse are arranged in bundles called muscular columns or sar- 

 costyles, and these again in larger groups, which, collected together, form the 

 fibre. The fibrillae are surrounded by the sarcoplasm, which surrounds also the 

 columns and groups of columns, being in these latter situations greater in amount 

 than between the fibrillse. So that on transverse section a muscular fibre is seen 

 to be divided into a number of areas, called the areas of Cohnheim, more or less 

 polyhedral in shape, and consisting of the columns of fibrillre surrounded by trans- 

 parent sheaths of sarcoplasm. And these areas are collected into larger or smaller 

 groups, which in the same manner are surrounded by transparent sarcoplasm. 

 Each area of Cohnheim presents a granular appearance due to the cross-section of its 

 constituent fibrillge, surrounded by a small amount of the hyaline sarcoplasm. The 

 fibrillae extend throughout the whole length of, and are parallel to, the long axis of 

 the muscular fibre. They present the following appearances in regular alternation : 

 (1) a dim prismatic or rod-shaped element, the sarcous element of Bowman ; (2) a 

 thin bridge, which joins the sarcous element to (3) a dark granule. Then again 



