77 



concentrations varying from Ph 5,5 to 8,5, showed a distinct 

 maximum of growtii between Pii 7.1 and 7,8 (figs. 1 to Oj. 

 Tlie rate of growlli decreased rapidly wilh increasing hy- 

 drogen ion concenlralion and hydroxyl ion eoneenlralion and 

 the curve ol)lained was neai'Iy symmetrical. The curves 

 I'caclied a maximum al Ph 7,1 and fell vei\v I'apidly on 

 l)()tli sides of lliis point always a little stee])er on the alka- 

 line side in spite of the fact that the resistance against the 

 alkalinilj was more marked. The type of curves were the 

 same in all experiments. By this method it was possible 

 only to investigate a short range of concentrations of the 

 hydrogen ion. because the coagulation process of the plasma 

 was interfei'ed with when the Ph was below 5,5 and above 

 8.5; sometimes i)recipilalions occurred — so it proved im- 

 possible to draw any conclusions from the experiments 

 beyond the said range. 



If the series of experiments was repeated by carrying 

 the fibroblasts into a new medium containing the same hy- 

 drogen ion concentration as used in the former culture 

 medium, it was observed that the absolute ino'ease of new 

 growth became less and less in the most alkaline and 

 most acid media, (fig. 7 and tables 10— llj. The descent of 

 the curve on both sides of the maximum became more abrupl 

 in the succeeding generations because of the retardation 

 of growth in the media with the highest alkalinity and 

 acidity; compare fig. 5 which represents the first passage 

 and fig. 6 which represents the fifth passage. 



By following the growth of fiblroblasts passage after pas- 

 sage, in media containing the same hydrogen ion concentra- 

 tion, it was observed that in the highest acidity (pH 5,5) 

 growth censed atler four Lo six passages. The !ibrobh>st.s' 

 showed more resistance to higher alkalinity, but at the 

 highest grade of alkalinity (pH 8,5) they grew for about 

 eight to ten passages. — The optimum growth occurred be- 

 tween pH 7,0 and 7.8. This was found also to be the 

 normal reaction of a mixture of plasma and embryonic 



