266 The Microscope. 



Fig. 52. — Part of a fiber showing a wavy contour. The 

 bottoms of the depressions apparently join the dark striae (Krause's 

 lines) in the middle of the light discs. The nuclei nn are outside 

 the sarcolemma, and one is dividing. From a long muscle of the 

 inside of the leg of a gray bat. Drawn with a 2 mm. Zeiss, 

 apochromatic, homogeneous immersion objective and ocular x4, in 

 optical section a little below the middle of the fiber. 



Figs. 53-55. — Transections selected from a series into which a 

 small portion, consisting of two fascicles, /, /, of the biceps fenioris 

 of the house mouse was cut. Fig. 53 is at a point 1^ mm. 

 from a tendon. Fig. 54 is 3^ mm. from the tendon. Fig. 55 is 

 13 mm. from the first tendon and 1 mm. from the other. The 

 same two fascicles are seen in each figure, but differ in form and 

 relative size. The fine lines indicate the secondary fascicles into 

 which they are divided, and these are not constant in form, number 

 or relative position. The dotted lines enclose a few tertiary 

 fascicles or fascicules, c, d, e, of which more and enlarged sections 

 are seen in the following figures. 



Figs. 5G-09. — Fourteen transections selected from the same 

 series as Figs. 53-55, showing the same fascicules c, d and e. Fig. 

 50 corresponding to Fig. 54, Fig. 68 to Fig. 55. These consecutive 

 figures are from points in the muscle varying from .2 to 2 mm. 

 apart, and intermediate and transitional forms occur between them. 

 Fig. 56. — Three distinct fascicules, which, up to this point in the 

 muscle (3f mm. from the tendon) have each been formed by the 

 union of two or more fascicules as distinct as these. Fig. 57. — The 

 fascicule c has become divided into c and c' by a septum. Fig. 

 58. — Two new septa appear in c and two in e, giving e, e\ e\ Fig. 

 59. — A septum appears in d, giving d and d'. Fig. 60. — The septa 

 in c disappear, and also the one between e'^ and a neighboring fasci- 

 cule. Fig. 61. — c is again divided by septa, in a somewhat different 

 manner fi'om the first division, into c, c', c', and e^ is again separate 

 from its neighbor. Fig. 62. — c and c* unite, and also e' and e*. 

 Fig. 63. — c is again- divided into c, c^ c^ and d' unites with a 

 fascicule at the left. Fig. 64. — c is divided anew, in another part, 

 into c and c* and d' separates from its neighbor. Fig. 65. — c again 

 divides into c and c\ Fig. 66 . — c' and c* unite, and also d and c^ 

 From this point the fibers diminish in number, and the fascicules 

 unite and disappear. Fig. 67. — c' and c* unite and e and e'. Fig. 

 68. — d^ disappears. Fig. 69. — e disappears. The remainder of 

 the sections to the tendon were not perfect enough to trace the 



