MUSCULAR CONTRACTION IN TISSUE-CULTURES. 205 



cells, even along the edge of the growth. Fixation causes the coagulation of the 

 cytoplasm along the muscle fiber in the form of a more or less straight fibril. In 

 the ends of the fixed muscle sprouts, however, many fibrils, both coarse and fine, 

 are formed by the coagulation of this material (fig. 10) . These fibrils may be straight 

 or curved in various ways, due probably to the amount of contraction of the mus- 

 cular substance. In some muscle buds the coagulated material resembled 

 the structure termed primitive myofibril by Godlewski (1902). 



CONTRACTION OF THE SKELETAL-MUSCLE CELL. 



The skeletal-muscle tissue, whether in the form of a muscle sprout, an 

 isolated fiber, or a myoblast, exhibited contraction as a rather rapid (3 to 120 times 

 per minute, Lewis, 1915) shortening and thickening of the muscular material, with 

 a tendency of the two ends to approximate each other. In the muscle fiber no 

 circular folds were observed along the length of the fiber, neither was there any 

 marked bellying out of the muscular protoplasm at any given region. No folds 

 were found around the myoblasts, but there was a thickening along the middle of 

 the cell (fig. 5) . In no case was a pendular movement observed, either by itself or 

 coincident with the shortening and 

 thickening of the muscle cell. It 

 might be stated that the phenome- 

 non of contraction, as shown by the 

 skeletal muscle, differed from that 

 characteristic of the amnion cell and 

 also from that exhibited by the heart 

 cells, in that it was neither a flowing 



. . "r FIG. 5. Skeletal myoblasts which were undergoing rythmical 



(amnion) nor a beating (heart) contractions. One cell with a rate of 4 per min., the other 



movement, but one that more nearly with f rat f e l 3 , P er n - c , ulture 5 n da >: s ol ? hom skeletal 



muscles of a 6-day cluck embryo. Oc. 4, oil-imm. 



resembled a straight twitch. Spon- 

 taneously contracting muscle fibers, and also myoblasts, were frequently found, and in 

 these the rhythmical contractions were exhibited for several hours. At times, how- 

 ever, the activity was induced by some form of stimulation (M. R. Lewis, 1915). 



OTHER CROSS-STRIATED MUSCULAR TISSUE. 



A number of the theories advanced to explain the phenomenon of contraction 

 of muscular tissue have been based largely upon the reactions and appearances of 

 the isolated sarcostyles from the wing muscle of the insect. The isolated sarcostyle 

 proved a fascinating field for experimental investigation, as may be inferred from 

 the numerous observations found in the writings of Krause (1873), Merkel (1872, 

 1873, 1881), McDougall (1897), and Schafer (1891, 1912); but it is difficult to 

 understand why certain agents, such as acetic acid following alcohol (Merkel), 

 should have been chosen to obtain results upon which conclusions were to be 

 drawn concerning the action of living tissue. In my observations marked changes 

 were brought about in the appearance of the sarcostyles by almost any change in 

 the medium surrounding them i. e., dilution, increase in osmotic pressure, increase 

 in the amount of any one of the salts constituting the medium, or the addition of 



