MUSCULAR CONTRACTION IN TISSUE-CULTURES. 



203 



the rhythmical contractions was rapid, about 70 to 120 per minute. Owing to the 

 rapid shortening and thickening, together with the slight pendular movement, the 

 phenomenon of contraction exhibited by the few entirely isolated cells observed 

 had the character of a distinct beat as though the single cell constituted in itself 

 a minute force pump rather than an infinitesimal part in such a structure. Figure 

 4 shows a few of the changes of form through which an isolated contracting cell 

 passed within the period of a few hours. This cell, although exhibiting contrac- 

 tions at the rate of 115 per minute, formed several pseudopodia while under observa- 



FIG. 4. Changes in 

 shape exhibited by 

 a heart-muscle cell 

 while undergoing 

 r h'y t h m i c a 1 con- 

 traction. Drawn 

 at intervals of 15 

 minutes. Rate 115 

 beats per minute. 

 Culture 48 hours 

 old from heart of 

 4-day chick em- 

 bryo. Oc. 4, oil- 

 iinin. 



tion. The cell was markedly refractive, there were no myofibrils present, and the 

 mitochondria and other granules were neither markedly different from those of 

 any other cell, nor did they undergo any change relative to each contraction of the 

 cell. 



COMPARISON WITH THE CELLS OF THE NORMAL HEART. 



An effort was made to compare the behavior of the heart cells in tissue cultures 

 with those of the normal heart. Preparations of the entire blastoderm (2 to 4 

 days' incubation) were made in the same manner as that used by Sabin (1917) 

 for the study of the development of the blood-vessels in the living chick embryo. 

 The beating heart was observed with ease, but it proved to be practically impossible 

 to analyze the part played by the individual cell because the coordination of the 

 mass of cells was perfect. The coordination of the beat of the cells of the explanted 

 piece, however, can be disturbed by the addition of calcium to the culture medium. 

 In one such experiment each cell acquired an independent contraction, so that the 

 result was an astonishing dancing of the individual cells without any coordinate 

 beat of the piece as a whole. This peculiar activity was caused by an extremely 

 rapid shortening and thickening, together with a slight pendular movement of each 

 cell. 



SKELETAL MUSCLE. 



Loeb (1899), Carrey (1905), Langley (1908), and Mines (1908) have each 

 discussed the contraction exhibited by isolated skeletal muscle in various media. 

 While the phenomenon continued for only a very brief interval of time in any of 

 the media used by these observers, nevertheless Locke's solution was found to be 

 the most favorable medium for experimental purposes. 



