SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 759 



For convenience the three symbols adopted here will be R.R. 

 (respiratory rate), O.G.R. (aerobic glycolysis rate), and N.G.R. 

 (anaerobic glycolysis rate), i c.mm. of extra carbon dioxide (from 

 the bicarbonate) corresponds to 0-004 mgm. of lactic acid, Warburg, 

 Posener & Negelein made many experiments to delimit accurately 

 the effect of pH, concentration of bicarbonate buffer and glucose, 

 temperature, presence of serum, etc., on the three entities: thus with 

 increasing j&H (6-7 to 7-8) the N.G.R. rose from about 7 to about 16. 

 But what more directly interests us is their comparative results for 

 different tissues, in the estimation of which they were careful to ob- 

 serve standard conditions (37-5°, 0-2 per cent, glucose, 2-5 x 10-^ % 

 bicarbonate, pH 7-66). They noted here yet a further entity, namely, 



^, ,^ , r- ■ lactic acid disappearing N.G.R. - O.G.R. 



the Meyerhof-quotient -. r^-^- ^ or — — 



respiration R.R. 



(M.Q^.), which gives a measure of the extent to which the lactic acid 

 formed is built up again into the glucose or the hexose-phosphate. 



The results of their experiments are given in Table 9 1 . A glance 

 at it shows several very important results. In the first place, the 

 Meyerhof-quotient is normal for all tissues studied, a fact which 

 Warburg regarded as evidence that the desmolysis mechanism, though 

 working unduly intensely in certain tissues (especially the neoplasms), 

 was normal in its nature. In every case, moreover, the rate of desmo- 

 lysis of carbohydrate, or rather the rate of accumulation of the lactic 

 acid, is higher anaerobically than aerobically, but tissues vary a 

 great deal in the extent to which this is so. In some cases, the per- 

 centage inhibition of lactic acid accumulation which occurs when 

 the tissue passes from anaerobic to aerobic conditions is great, per- 

 haps as much as 95 per cent. But in other cases, and these include 

 the neoplasmatic tissues, the inhibition due to the letting in of oxygen 

 is only small. Thus the rat carcinoma has a glycolytic power 1 24 times 

 that of adult blood, 200 times that of resting frog muscle, and 8 times 

 that of acting frog muscle. As for the respiratory intensity, it varies 

 quite independently of the other entities, and is sometimes large, some- 

 times small. As the extreme instance of the glycolytic tissue, Warburg 

 cited yeast, which desmolyses large amounts of sugar aerobically as 

 well as anaerobically. As the extreme instance of the respiratory 

 tissue, there is Pasteur's mould, Mucor mucedo, and the table provides an 

 example, rabbit pancreas or submaxillary gland, for instance, allowing 

 no lactic acid at all to accumulate aerobically. It was obviously 



