DEPARTMENT OF EMBRYOLOGY. 91 



In our last report reference was made to the study of the effect of 

 ether vapor upon growing tissues. Since then a series of related ex- 

 periments has been made (Hogue, W. H. Lewis, and M. R. Lewis) 

 in which the environmental conditions have been changed in various 

 ways, including the introduction of bacteria. 



In order to test the effect of different concentrations of hypotonic 

 and hypertonic solutions upon normal cells, Dr. M. J. Hogue explanted 

 pieces from the heart tissue of chick embryos in Locke-Lewis solution 

 containing varjdng amounts of sodium chloride. Two types of con- 

 nective tissue are characteristic of such growths— fibroblasts and meso- 

 thelial cells. The former were selected for study, being more numerous 

 and more sensitive to the solutions. These cells may either migrate 

 out into the medium or grow as a reticular network, and their growth 

 differs in these respects in the different solutions. Using hypotonic 

 solutions of three strengths, the sodium-chloride content being respect- 

 ively 0.54, 0.45, and 0.225 per cent, it was found that the weakest 

 solution gave no growth whatever. In the intermediate solution the 

 cells grew normally and resulted in large growths in both reticular and 

 migratory formation, surviving as long as 12 days. In the 0.54 per 

 cent solution the growth, as compared with the controls, was very 

 rapid, but the cultures did not live as long. The cause for the increased 

 migration exhibited by such preparations seems to be the search for 

 food, the deficiency of food material in the medium acting as a stimulus. 

 This would also account for the striking fact that in all of these cultures 

 the cells nearest the explant were the first to die. This is explained on 

 the ground that the search for food stimulates motility; hence the cells 

 throw off more than the usual amount of waste matter. This becomes 

 so great near the explant and the supply of food so scarce that the cells 

 in this vicinity succumb, while those which have migrated out into the 

 medium are freer from waste products, get more oxygen, and conse- 

 quently live longer. This condition is just the reverse of what happens 

 in normally grown and hypertonic cultures. In these, cell death begins 

 at the outer edges and progresses inward towards the explant. 



Three series of experiments were made with hypertonic solutions 

 containing respectively 1.8, 1.5, and 1.2 per cent sodiiun chloride. 

 In the strongest there was no growth whatever, as was the case with the 

 weakest hypotonic solution. INIoreover, when added to cultures that 

 were doing well in the normal Locke-Lewis medium, the cells were all 

 killed within a few hours. In a solution containing 1.5 per cent sodium 

 chloride onlj^ 9 per cent of the cultures grew. In these, migration was 

 not extensive and very few showed reticular growth. The cell struc- 

 tures as a whole appeared much the same as in normal growths. When 

 added to cultures that were gro^\dng well in the same medium or in 

 normal Locke-Lewis solution the cells were killed by it. Growth in a 

 1.2 per cent solution was very good, though slower than in the controls, 



