SECT. 6] 



OF THE EMBRYO 



86 1 



metrically. Thus Gueylard & Portier employed this method, obtaining 

 the curve shown in Fig. 214, but not putting forward any explana- 

 tion for the sharp trough passed through about the 15th day. A much 

 more complete piece of work, which involved the crushing of the cells 

 before they were brought into contact with the indicator, was that of 

 Murray. His figures are given beside those of Gueylard & Portier in 

 Fig. 214, and it is unfortunate to note that, although his period was 

 better investigated than theirs, the two do not overlap completely, so 

 that we cannot tell whether Murray would have got the low values 



vV 



,OS^ 



f^/^ ^•-^ V\'<:P 



library)^ 



D&ys 



10 a 14 16 

 Incub«tion e^ 



Fig. 215. 



about the 15th day if he had gone on. He found that a regular 

 S-shaped curve (dotted in Fig. 2 1 4) would fit them, but it is unUkely 

 that this was more than mere coincidence. As for the points of 

 Friedheim and of Yaoi, they disagree with both the other sets. 



Murray, however, estimated some other entities as well as the pH 

 by crushing the cells, and it will be best to describe his results here. 

 Fig. 2 1 5 shows the molar concentration of chlorides (determined by 

 the Van Slyke method) in the embryonic tissues related to age, and 

 Fig. 216 the molar concentration of total carbonic acid similarly 

 plotted. Murray was inclined to correlate the increasing acidity of 

 the tissues with the accumulation of the carbon dioxide of cata- 

 bolism, but this, though a sufficient explanation for his own few 



