932 



GENERAL METABOLISM 



[PT. Ill 



It is interesting to enquire what is the absorption rate of the 

 embryo at the different stages of its development In the case of the 

 mammal this is again impossible, for we know nothing quantitative 

 about the substances burned by it. Its storage rate can, of course, 

 easily be calculated from the figures of Michel or Fehling, thus : 



Months 



5 



9 



Weekly percentage increment 

 of nitrogen storage in the 

 human embryo 



0-22 



0-20 



O From dry wt.and oxygen 



consumption 

 ® From chemical analyses 



•7- 0) 

 •6I--0 



but such a calculation tells us nothing more than that the percentage 

 growth-rate is decHning, a fact 

 already well known. The true 

 absorption rate has only been 

 calculated for the chick embryo. 

 Murray obtained it in 1926 from 

 his determinations of carbon 

 dioxide excreted and oxygen 

 taken in by the chick embryo 

 from the 5th day of incubation 

 onwards by simply adding the 

 rate of storage in terms of weight 

 (see p. 384) to the rate of re- 

 spiratory exchange, likewise in 

 terms of weight measured by oxy- 

 gen usage. His values are shown 

 in Fig. 253, where the rate of dry 

 solid absorption per gram of em- 

 bryo (dry) per day is plotted 

 against the age. Evidently the curve falls rapidly 

 the equation: 



Solid stored + solid burnt = solid absorbed 



can also be demonstrated in another way, namely by adding together 

 the results of all the chemical analyses of protein, fat and carbohy- 

 drate and ash. Of these we have very reliable figures for the amounts 

 of carbohydrate, protein and fat stored, and for the amount of protein 

 combusted, but the amounts of fat and carbohydrate combusted have 

 never been directly measured, and must therefore be approximated. 

 Nevertheless it was of interest to calculate the theoretical absorption 



E 

 - cr> 



Days -^5 



10 

 Fig- 253. 



But the use of 



