SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 



765 



compared the activities of various tissues in this direction, obtaining 

 the following results : 



Rat thyroid 



Rabbit submaxillary 



Rat liver 



Rabbit pancreas ... 



Rat thymus 



Rat testis 



Chick embryo (5th day) 



Rat carcinoma 



Rat grey matter ... 



Rat retina ... 



Cubic millimetres of am- 

 monia produced (in glucose- 

 free Ringer) /milligrams of 



tissue X hours N.G.R. 



o 2 



0-03 3 



0-07 3 



on 3 



0-31 8 



003 8 



0-56 23 



0-9 31 



1-4 . 19 



It is evident that all the tissues concerned prefer to combust carbo- 

 hydrate if they can get it, but if not they will combust protein. 

 It would be very interesting to know how this property varies during 

 development in the chick. A certain parallelism is to be observed 

 between the anaerobic glycolysis rate (not the R.R.) and the am- 

 monia-production rate in aerobic glucose-free conditions. The ad- 

 dition of glucose abolished the ammonia production both aerobically 

 and anaerobically. 



The next important paper was that of Negelein, who devoted 

 himself particularly to the 

 examination of the changes 

 taking place in respiratory 

 characteristics during em- 

 bryonic growth. Chick em- 

 bryos, as Warburg, Posener 

 & Negelein had already 

 found, produced anaerobi- 

 cally 9 per cent, of their 

 weight in lactic acid per 

 hour; rat embryos, Negelein 

 now found, produced only 

 between 3 and 7 per cent. But all depended on the time of develop- 

 ment, for in the earlier stages rat embryos had a figure of about 

 14 per cent. The amniotic membranes and the chorion were found to 

 have an even larger figure, as much as 19-6 per cent., i.e. fully as high 

 an N.G.R. as neoplasms. The curve which resulted from Negelein's 

 observations appears in Fig. 169. The measurements were nearly all 



Trockengewichteines Embryos (mgr) 

 Fig. 169. 



