THE ECTOPLASM 



ing them. These suggestions are consistent with the well- 

 estabUshed findings of studies made on both types of 

 muscle-cells by the method of tissue-culture devised by 

 Harrison and with the fact that in the muscle-cell the 

 ectoplasm is preponderant. Also, they stand in accord with 

 our knowledge of ectoplasmic structure in cells generally. 



The smooth muscle-fibre, an elongated slender spindle- 

 shaped cell, reveals itself in fixed preparations as possessed 

 of fine longitudinal threads, fibrils or myofibrils. Lewis and 

 Lewis were unable with the use of either bright- or dark- 

 field illumination to observe any fibrils in living smooth 

 muscle-cells grown in tissue-culture. According to them, 

 large flat cells seldom contract whereas the elongated and 

 band-like ones sometimes exhibit rhythmic contraction. 

 These latter show ectoplasmic processes. 



Very much elongated overlapping processes may simulate 

 fibrils when parallel to the long axis of the cell. In many 

 places the cells seem to spread out under considerable ten- 

 sion, and it appears to be along the lines of tension that the 

 contractile substance coagulates into fibrils of various sizes. ^ 



From what is known of the contractile power of ectoplasmic 

 processes of cells generally in tissue-culture, it is safe to 

 conclude that the contractility of the smooth muscle-cell 

 is likewise inherent. I suggest that the pictures of fibrils 

 obtained in fixed preparations represent ectoplasmic pro- 

 cesses somewhat altered by the action of the reagent 

 employed to fix the cell. 



Striated muscle differs from smooth by showing alter- 

 nate light and dark bands traversing its long axis. The 

 exact structure of striated muscle remains in question. 

 Since it begins its development as smooth muscle, it would 

 seem most profitable to attempt an elucidation of its 

 structure through study of its developmental stages. 



^ Lewis and Lezvis^ 1924. 



79 



