76o RESPIRATION AND HEAT-PRODUCTION [pt. iii 



very important that Warburg found the tissue of neoplasms to behave 

 unUke muscle and like the yeast-cell. But it is more interesting for 

 the present purpose to note that he found the chick embryo (from 

 the 3rd to the 5th day of development) to be different alike from 

 adult and from neoplasmatic tissue. In its efficiency at removing 

 lactic acid when allowed air, it resembled muscle, but its general 

 metabolic level was of course higher and appeared in the big R.R. 

 The relation between aerobic glycolysis (O.G.R.) and R.R. is also 

 interesting; thus from the last column it appears that the chick 

 embryo produces only o-i mol. of lactic acid for every mol. of 

 oxygen taken in — a very different state of affairs from the tumour- 

 cells, which will produce as much as 3-9 mol. of lactic acid for every 

 mol. of oxygen, though it is not unlike the adult tissues, which 

 occupy an intermediate position. Warburg found that by adding a 

 trace of hydrocyanic acid to the medium containing the embryonic 

 tissues he could, as it were, put a spoke into the wheels of the oxida- 

 tion mechanism, and bring about a state of affairs resembling that 

 of tumours. Thus he was able to send up the O.G.R. of the 4th-day 

 chick embryo from i-i to 12-0, to bring down the percentage in- 

 hibition from 96 to 45, and to make the embryo produce 3-4 mol. 

 of lactic acid for every mol. of oxygen taken in. This was a good 

 imitation of a malignant carcinoma. Moreover, tumour-cells + hy- 

 drocyanic acid gave the same O.G.R, as N.G.R., showing that 

 oxidations had been entirely depressed. The benign tumour-cells, 

 with their O.G.R./R.R. of about 0-9 could, he found, be equally well 

 imitated by incubating embryonic tissue anaerobically for some time 

 before beginning the experiment. But though he was able thus to 

 induce in embryonic material the characteristics of neoplasmatic 

 tissues, he was not able to reverse the process, or to ascertain how 

 it was that these characteristics were retained for a great length of 

 time by some cells. Such observations as these acquire no Uttle 

 significance from the fact that sarcomata can be produced in adult 

 animals by injecting embryo pulp with arsenious acid (Carrel; White; 

 Askanasy; Mcjunkin & Cikrit; denied by Begg & Cramer) with tar 

 (Carrel) and with indol (Carrel). 



The metabolism of the neoplasms was called by Warburg that of 

 disorganised growth, and the metabolism of the embryo that of 

 organised growth. These distinctions are of interest in view of the 

 work of Byerly (see p. 607), and have a relation to much recent 



