758 THE RESPIRATION AND [pt. hi 



4*20. Embryonic Tissue-respiration and Glycolysis 



The study of the respiration of embryonic tissues in vitro has taken 

 a great step forward through the work of Warburg and his col- 

 laborators, who have related the oxygen consumption of tissues in 

 a very interesting way with the type of metabolism going on in them. 

 Preliminary researches on technique by Warburg and by Minami 

 showed that it was possible to determine on the same material the 

 oxygen consumption per gram per hour and the amount of lactic 

 acid produced both in air and in nitrogen. The lactic acid produced 

 was estimated by using bicarbonate buffer solutions, and calculating 

 from the amount of "extra carbon dioxide" given off^ In the first 

 paper of the series Warburg, Posener & Negelein studied the relations 

 between respiration and glycolysis in a number of tissues. Their basic 

 concepts were analogous to those universally employed with regard 

 to muscle metabolism. In the linked reactions 



Glucose — ?► Lactic acid — s-COg and H^O 



one of the two may be slower than the other ; the oxidative power 

 of the tissue may be able to remove the lactic acid as fast as it is 

 formed, or conversely, oxidation may be the slower process and lactic 

 acid will tend to accumulate. In intact muscle, as has long been 

 known, the desmolysis and oxidation processes are controlled so that 

 anaerobically lactic acid is formed in great amount, but aerobically it 

 is rapidly oxidised. In chopped muscle, the desmolytic process gets 

 out of control, and nearly as much lactic acid accumulates aerobically 

 as anaerobically; in other words, the oxidation process cannot keep 

 pace with it. By the study of the relative activities of these mechanisms, 

 Warburg and his associates were able to classify tissues to a con- 

 siderable extent. In this work they used three symbols, defined as 

 follows : 



^ c.mm. of Oo used up , • ^- \ r, n 



Q^o, = 7^^^ r-^- — respiration) R.R. 



mgm. of tissue x hours 



0°^ = c-mm. extra GO, given out in O, (^..^bic glycolysis) O.G.R. 

 ^co, mgm. of tissue x hours 



„ N^ ^ c.mm. total ^ CO, given out in N, (anaerobic glycolysis) 

 ^coa mgm. of tissue x hours N.G.R. 



^ Assuming the R.Q.. of the tissue to be unity. 



^ Anaerobically there can be no "extra" COj because respiration in the sense of 

 oxygen-consumption is not proceeding; all of it must be due to lactic acid formation. 



