7i6 



THE RESPIRATION AND 



[PT. Ill 



consumed rather more oxygen and gave off rather more carbon 

 dioxide than the controls, but after that exactly the reverse relation 

 held good, the cross-over taking place on the 12th day (see Fig. 155). 

 As has already been mentioned (p. 539), the weights of the 

 embryos from the injected eggs were always within minute limits 

 the same as those from the controls. It is therefore evident that the 

 metabolic rate must have been intensified during the first period, 

 and diminished afterwards. Evidently in Hanan's experiments the 

 developmental machinery was 

 dissociated into its components, 

 metabolic rate being aflfected but 

 not growth-rate. 



In a later paper, Murray went 

 on to study the oxygen intake 

 of the developing egg by ac- 

 curate methods involving the use 

 of a differential manometer in 

 which convection currents were 

 set up by leading thin-walled 

 rubber tubes containing cold 

 water past the vessel and in con- 

 tact with it. Murray neglected 

 to give the figures he obtained 

 for cubic centimetres of oxygen 

 used per egg per day, and only 

 published the metaboHc rate, 

 but the former can be calcu- 

 lated. In Fig. 156 they are 

 shown, so that here also the 

 American values come higher 



9 10 1112 13 14 15 16 17 



Fig. 155- 



than the Danish ones. Murray's 

 metabolic rate for oxygen appears in Fig. 143, where the cubic centi- 

 metres of oxygen used per gram (wet weight) of embryo per day are 

 plotted against the age from 5 to 19 days. Again, there is a notable 

 decline, but the curve, as drawn, does not follow the carbon dioxide 

 values very well, and presents an S-shaped appearance instead of being 

 concave to the abscissa, as Murray's rule requires. However, the 

 burden of the highest part of the curve rests on one point only, and, if 

 that were wrong, the appearance of the whole would resemble that of 

 the carbon dioxide metabolic rate curve very closely. Murray himself 



