974 ENERGETICS AND ENERGY-SOURCES [pt. iii 



Evidently the temperature exercises no effect on the proportion of 

 energy used for storage and that used for combustion. More or less 

 analogous results had previously been found for the development of 

 Proteus vulgaris by Rubner, for muscular contraction by Hill, for the 

 growth of Sterigmatocystis nigra by Terroine & Wurmser, and for the 

 germination of seeds by Terroine, Bonnet & Joessel. The invariability 

 of the A.E.E. of embryonic growth would seem, then, to be a special 

 case of a general biological law. 



The next question which arises is whether the efficiency varies from 

 time to time during the development of the embryo ; we have already 

 seen that the P.E.C. shows such a variation. Table 124 gives the 

 calculations for determining this (Needham). The increments of 

 calories, i.e. the amounts of potential energy stored in the embryonic 

 body each day, are checked against the energy present in the extra- 

 embryonic part of the t§^g as determined with the bomb calorimeter 

 by Tangl & von Mituch. It will be seen that the rest of the egg loses, 

 in addition to combustion, 250 cal. between the 8th and the 9th days, 

 while the embryo gains 232; a sufficient agreement. The figure of 

 34,000 cal. seen at the bottom of Col. 4 representing the number of 

 calories contained in the finished embryo agrees sufficiently well with 

 the value given by Tangl of 32,000; the latter was measured directly, 

 the former was obtained by the addition of all the increments. 



Cols. 6 to 9 give the figures relating to the energy lost in combustion. 

 This is obtained, assuming that 100 per cent, instead of the true 92 

 per cent, of the total solid burnt is fat, and that i gm. of fat pro- 

 duces on its combustion 9300 cal. The total of this column amounts 

 to 17,000 cal., not very far from the 16,500 cal., the Ea. of Tangl. In 

 Col. 10 Tangl's values for Col. 9 are given, and it may be noticed 

 that they are close to the newer ones. An error exists here owing to 

 the fact that no account has been taken of the energy left behind in 

 incompletely combusted materials, but as the chief of these is uric 

 acid, and — using the data of Stohmann & Langbein for the calorific 

 value of uric acid, 2750 cal. per gm. mol. — the calories locked up in 

 this way only amount to 16 on the loth day, or much less than i per 

 cent, of the total combusted; this error is neghgible. Finally Col. 1 1 

 shows the A.E.E., which is diagrammatically represented in Fig. 260. 

 Starting at a low level, it slowly rises, gaining in speed till at the 14th 

 day it is rising rapidly, but soon afterwards it falls off. The value for 

 the whole of development works out at 66-5, which is exactly what 



