CROSS STRIATED MUSCLE IN TISSUE CULTURES 185 



shaped bodies. They stain dark with iron hematoxyhn and 

 red with Mallory's stain. In favorable specimens, these spindles 

 were seen to fray out in places into fine striae similar to those 

 composing the cytoplasm (figs. 6, 7, 8, 10, 11). Such spindles 

 have not been observed in the living buds. 



Specimens fixed with acetic acid combinations and especially 

 with acetic acid vapor give pictures of fibrils and other struc- 

 tures within the muscle buds, which are not present in the living 

 cultures. Such methods are of course entirely useless so far 

 as the study of the optical structure of the cytoplasm is con- 

 cerned. The fibrils 'brought out' by the acetic acid are espe- 

 cially marked in that part of the muscle bud connecting the 

 amoeboid end with the expl anted piece. This portion of the 

 muscle bud is evidently under considerable tension as we have 

 already noted. It is probable that coagulation of the cytoplasm 

 when in a state of stress or pull takes place in lines parallel to 

 this stress and hence the formation of the longitudinal fibers. 

 Under such conditions the fibers brought to view are no indica- 

 tion whatsoever of their being differentiated structures in the 

 cytoplasm. 



The mitochondria are especially abundant in the muscle buds 

 and are arranged longitudinally between the fine longitudinal 

 striae. They are smaller than those in the mesenchyme cells 

 and in the healthy fibers do not show the same irregular arrange- 

 ment. It is rather difficult to make them out in the living buds. 

 With Janus green, however, they usually appear as strings of 

 minute granules of varying lengths and sometimes as long 

 threads which seem to taper off at either end to the limits of 

 visibility. The mitochondria are best seen in the enlarged 

 protoplasmic end of the buds and undoubtedly contribute to 

 the appearance of longitudinal striation. 



Fig. 12 Isolated muscle fiber from the same culture as the above. 



Fig. 13 Isolated myoblast from the cultures from the wing of an eight day 

 chick embryo cultivated two days in 80 per cent Locke's solution plus 20 per 

 cent bouillon; plus 5 per cent dextrose. X 525. 



Fig. 14 Veil-like spreading out of the stem of a muscle bud from a two day 

 culture of the muscle from the wing of an eight day chick. Locke's solution plus 

 few drops yolk plus Co per cent dextrose. X 455. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 2 



