SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 



657 



the nature of their integration. At present we are only uncovering, 

 as if by a kind of dissection process, the various contributory systems, 

 such as those represented in Murray's diphasic schema for the chick. 

 Shearer found that in i hour i million unfertilised eggs (correspond- 

 ing approximately to 8 mgm. 

 egg nitrogen) consumed 15-1 

 c.mm. of oxygen and gave off 

 at the same time 0-067 gm. cal. 

 at standard temperature and 

 pressure. After fertilisation the 

 same quantity of egg-substance 

 consumed 86-4 c.mm. of oxygen 

 and liberated 0-3976 gm. cal. 

 heat together with an amount 

 of carbon dioxide equivalent to 

 a respiratory quotient of 0-92. 

 These figures were afterwards 

 gone over again by Rogers & 

 Cole, who desired to introduce 

 even more accurate methods, 

 and to take readings at short intervals over considerable periods of 

 time. Rogers & Cole only published one paper, most of which was 

 taken up with problems of technique. In Shearer's experiments, 

 the vacuum flasks were undergoing a gradual fall of temperature 

 throughout the experiment, and 

 the difference in rate of fall 

 between the control flask and 

 the flask containing the experi- 

 mental material gave the heat- 

 production of the eggs. Rogers 

 & Cole, however, used a dif- 

 ferent method, by which the fall 

 was much slower, and therefore 

 much longer experiments could 



Corrected carve 

 Extrapolabion of the 



ear(y peurt erf the curve 



be_yoncL 50 minabes 



Fig. 119. 



50 100 



Minutes after fertilisation 



Fig. 



be carried out. Fig. 119 shows one of their experiments. The total 

 number of eggs used was 3-9 millions. The curve well demonstrates 

 the absence of any variations due to cleavage. In Fig. 120 the 

 average rate of heat-production in calories per hour per million 

 eggs from all their experiments is given. It is probable that not 



