CROSS STRIATED MUSCLE IN TISSUE CULTURES 177 



and continue to grow out in this manner (figs. 1, 3, 4, 8). Buds 

 widely sejmrated at their origin often fuse at some distance 

 from the explanted piece when their direction of outgrowth is 

 such as to bring them into contact with each other (fig. 3). 



The muscle buds very often send off branches of different 

 sizes, such branches project at various angles and often unite 

 with other branches or buds. This may result in the formation 

 of more or less complex networks (figs. 3, 4). In some cases 

 the anastomoses are probably without direct continuity of the 

 cytoplasm but in many cases there is undoubted continuity of 

 the cytoplasm (fig. 8). 



There is a very curious resemblance between the outgrowths 

 of muscle and nerves in the tissue cultures. The formation of 

 protoplasmic buds with numerous long processes that are con- 

 tinually changing and the migration of this mass away from the 

 explanted tissue pulling out the muscle or the nerve fiber present 

 somewhat similar phenomena. The two differ markedly in one 

 important respect. The nerve outgrowths are entirely without 

 nuclei while the muscle fibers contain many nuclei both in the 

 protoplasmic buds and in the connecting fiber. 



Different muscle buds, although they have the same general 

 character, vary considerably in the more detailed appearances. 

 Figures 1 and 2 show long slender outgrowths from a piece of the 

 leg muscle of a seven day chick embryo. The two explanted 

 pieces were from the same leg and planted in the same medium 

 (one-half Locke's plus one-half bouillon plus 0.5 per cent dex- 

 trose). In figure 1 the ends are rather broad and fan-shaped 

 while in figure 2 they are narrow or pointed. There are more 

 anastomoses in the former culture than in the latter. In figure 

 2 there are to be seen many free fibers with one or more nuclei. 

 Th se fibers are very slender, pointed at either end and have the 



Fig. 3 Muscle outgrowth from an explanted piece of the leg of a nine day 

 chick embryo cultivated in Locke's solution plus bouillon plus 0.5 per cent dex- 

 trose plus 2 per cent distilled water for four days. Osmic acid vapor, iron he- 

 matoxylin. The muscle buds have not extended out nearly as far as the mesen- 

 chyme. Several large isolated fibers are to be seen, also anastomoses of muscle 

 buds. X 100. 



