SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 



757 



These figures demonstrate conclusively that the fall in metabolic 

 rate, which is evident in the case of the intact organism, can also 

 be seen when its tissues are considered in isolation, and can hardly 

 therefore be due to the falling relative surface. 



The fact that the oxygen consumption related to loo gm, of pro- 

 tein behaved in the same way as when related to weight was taken 

 by these authors as evidence in favour of their contention that there 

 exist in the cell "albumines de reserve", or paraplasmatic proteins, 

 and therefore that the total nitrogen cannot be regarded as repre- 

 senting the active protoplasmic mass. They regarded the demonstra- 

 tion of LeBreton & Schaeffer, that the chemical nucleoplasmic 

 ratio decreased during development, as a further support for that 

 view. The more paraplasmatic protein present, the less the nucleo- 

 protein in proportion. Finally, they adduced the decreasing water- 

 content which seems to be so universal an accompaniment of the 

 growth and ageing of protoplasm (cf Ruzicka's "law of protoplasmic 

 hysteresis") as tending in the same direction. As they pointed out, 

 I gm. of dry substance is dissolved or dispersed in 17-2 gm. of water 

 in the 4th day chick embryo, in 3-2 gm. of water at the time of 

 hatching, and in only 2-1 gm. in the adult hen. 



Terroine & Roche, on the other hand, investigating the in vitro 

 respiration of tissues, got results which differed from those of Kayser, 

 LeBreton & Schaeffer. They did not concern themselves with the 

 same organism at different ages, but with different organisms of 

 various sizes (homologous tissues of homoiotherms) . Their figures 

 were as follows: 



Table 90. 



There was evidently no relation at all between the in vitro respiration 

 of the tissues of the diflferent animals, in spite of their different heat- 

 production in vivo. It is much to be wished that further work could 

 be done along these lines. 



