MUSCULAR CONTRACTION IN TISSUE-CULTURES, 



BY MARGARET REED LEWIS. 



The solution of the problem of the structure and behavior of muscular tissue 

 has been frequently undertaken either from the standpoint of detailed and com- 

 plicated cell architecture or from that of the mechanics of dead material. It is by 

 no means claimed that the observations herein recorded solve this most interesting 

 problem; nevertheless the results show that it is possible to consider the question 

 entirely from the standpoint of living material and at the same time to be able to 

 disregard to a great extent the complicated structure of differentiated muscular 

 tissue. In other words the mechanism to be observed can be reduced to the simple 

 terms of a single slightly differentiated, living cell maintained under observation 

 throughout experimentation. 



METHOD. 



Although a new procedure, the tissue-culture method is well known, in view 

 of the fact that when it was first used conclusive results were obtained in two of 

 the important problems of anatomy and physiology i. e., that the axons grow out 

 from the nerve cells (Harrison, 1910) and that the heart muscle is capable of inde- 

 pendent contraction (Burrows, 1912). The method used in the present experi- 

 ments, while similar in most respects to that of Dr. Harrison and also that of Dr. 

 Burrows, was devised for the study of the cells of the blood, bone marrow, and 

 spleen, in relation to tuberculosis, independent of the work of the above authors. 

 The original solution contained agar. Since it was found (Lewis and Lewis, 1912) 

 that the presence of agar is not necessary for growth of the cells, the Locke-Lewis 

 solution, modified (M. R. Lewis, 1916) according to the species of animal and also 

 according to the osmotic pressure of the tissue to be explanted, has been employed. 



Tissues from chick embryos of 4 to 12 days' incubation were used for the 

 cultures. The medium was Locke-Lewis solution (90 c.c. of NaCl 0.9 per cent -f 

 KC1 0.042 per cent + CaCl 2 0.025 per cent + NaHCO 3 0.02 per cent + 10 c.c. 

 of chicken bouillon + 0.25 per cent dextrose; Lewis and Lewis, 1915). Aseptic 

 conditions were maintained throughout. The embryo was removed from the egg 

 and placed in a petri dish containing 20 c.c. of warm solution. Pieces of the tissues 

 to be explanted were removed, washed through one or more changes of warm 

 medium, and cut up with sharp scissors into pieces about 0.5 mm. in diameter. 

 Each piece was then placed on the center of a cover slip, part of the drop drawn 

 off, and the cover slip sealed on to a vaseline ring around the well of a hollow- 

 ground slide. Cultures thus prepared were kept in an incubator at 39 C. All 

 microscopical observations and experiments were made in a warm box at 39 C. 



The cells began to migrate out from the explanted piece within a few hours. 

 At the end of 18 hours a zone of cells, usually only a few cells deep but often wider 



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