208 MUSCULAR CONTRACTION IN TISSUE-CULTURES. 



granules present in these cells, nor were myofibrils observed. Pseudopodia were 

 formed by the cell regardless of the fact that it was undergoing rhythmical 

 contraction; so that while there is a change in the position of the protoplasm during 

 contraction, it is not dependent solely upon those factors which are involved in the 

 formation of pseudopodia (Verworn, 1895). 



A few experiments with various fats and soaps were suggested by Quincke's 

 theory of protoplasmic motion. These showed that, while it was possible to cause 

 the formation of pseudopodia (i. e., blebs of clear protoplasm) this change in the 

 position of a given portion of the protoplasm was not accompanied by contraction 

 of the cell. One of these experiments was as follows: 



A minute drop of oleic acid was placed in the medium surrounding an amnion 

 smooth-muscle cell. This caused the withdrawal of the intercellular bridges, so 

 that while the cell remained more or less spread out, it appeared as a somewhat 

 elongated, granular cell with knobs of non-granular protoplasm along the sides. 

 From the region of the knobs blebs of clear cytoplasm, which appeared to be much 

 more fluid than that of a normal cell, were rapidly extended and retracted, only 

 to form again in the same or another region. This activity continued for several 

 hours. Frequently, as many as four or five such areas of bleb formation were 

 observed along the surface of a given cell. The protrusion of the blebs, notwith- 

 standing their large size in some cases, was not accompanied by a shortening of 

 the cell, nor was a current of protoplasm induced towards the region from which 

 the bleb was extruded. This activity, while interesting in itself, did not in any 

 manner resemble that of contraction. 



In regard to the theory that surface tension plays a part in the phenomenon, 

 the following experiment is rather interesting. Certain inactive amnion smooth- 

 muscle cells were touched with a delicate glass bristle. 1 The cell touched immedi- 

 ately drew together, causing numerous swellings or folds to form on its surface. 

 These resemble the blebs described during mitosis of the cell (Lewis and Lewis, 

 1917). The folds shortly disappeared, after which rhythmical contraction was 

 initiated and continued to be exhibited for some time. However, this is but another 

 way of stating that mechanical stimulation induced contraction. 



Changes in the osmotic pressure of the medium, such as were suggested by the 

 experiments of Beutner (1913), did not sufficiently influence the contraction of the 

 muscle cells in cultures to enable one to draw any definite conclusions. No results 

 were obtained such as would show that the process taking place during contraction 

 of the muscle cells in cultures is comparable to that supposed by Lillie (1901) to 

 take place during the movement of the cilia of certain ctenaphores. Rhythmical 

 contractions were exhibited for many hours by the muscle cells in tissue cultures, 

 but it is impossible to estimate what changes may have occurred in the medium 

 immediately surrounding the cell, due to the movements of the cell itself or to 

 chemical interchanges, such as between the air and the medium, waste products 

 and the solution, etc. 



From the above observations it might almost be inferred that it is a normal 

 procedure for embryonic muscular tissue to undergo contraction. While in the 



1 This experiment was performed by Dr. Robert Chambers. 



