DISCUSSION ON TUMOR RESPIRATION 243 



be desired. Two more types of homologous tissue are presented in 

 Table 1 by the data on regenerating hver and embryonic hver, both 

 of which tissues may at certain stages attain growth rates even 

 greater than that of liver tumor. The data on regenerating liver are 

 very striking in that they show, as compared with normal adult liver, 

 no appreciable alteration in any of the metabolic values studied. In 

 the case of the very young rats, the regenerating Q^^a value is 

 slightly increased, but mainly as a matter of neonatal age rather 

 than of regeneration. Regenerating liver is indeed a remarkable case, 

 demonstrating that tissue growth may take place without appreciable 

 glycolysis, and at the expense, even, of unchanged oxygen consump- 

 tion; for the growth increase in liver tissue (on a water-free basis) 

 may attain 50 to 100 per cent per day during the most active phases 

 of regeneration at about two to three days after partial hepatectomy, 

 when mitotic figures are most numerous, several being visible on a 

 high power field, or even more than would be found with a butter 

 yellow liver tumor. Orr and Stickland (13) reported that the glycoly- 

 sis of regenerating liver was not appreciably different from that 

 of the normal livers they examined, but in these data the issue is 

 again confused and rendered indefinite by their exceedingly high and 

 variable normal liver values. 



A third type of homologous tissue is the rapidly growing embry- 

 onic Hver. Tamiya (16) showed over a decade ago that there is a 

 marked rise in the anaerobic glycolysis of chicken embryo livers 

 the younger the embryo and the smaller the liver (at least back to a 

 very early stage or microscopic size). The recent experiments of 

 J. Langdon Norris (11, 12) give essentially the same results for 

 embryonic rat livers as for the embryonic chicken livers. Contrary, 

 however, to opinion held since the work of Tamiya (16) and Hawkins 

 (9) that embryonic liver in particular and growing tissues in general 

 show considerable anaerobic glycolysis, the histopathologic sections 

 taken by Norris (illustrated elsewhere, 11, 12) show that the smaller 

 the embryonic livers and the greater the anaerobic glycolysis, the 

 greater and in parallel manner is the extent of haematopoesis, which 

 in the extreme may amount to an estimated 70 to 80 per cent of the 

 liver, involving mainly erythropoietic cells (with some megakary- 

 ocytes and myelogenic cells). The metabolism of these nucleated 

 erythropoietic cells has not yet been measured directly, but two 

 comparable types of nucleated erythroid cells are available for com- 

 parison, namely, the chick bone marrow erythroblasts produced by 

 acetylphenylhydrazine injections and the normal rabbit bone mar- 



