154 PATTERNS AND PROBLEMS OF DEVELOPMENT 



moved from the ventral marginal zone of the blastopore. Also, the CO^ 

 production of the isolated dorsal lip region is distinctly higher than that 

 of an equal cell volume from the ventral marginal zone (J. Brachet, 1934a, 

 b). Later determinations by Waddington, Needham, and Brachet (1936) 

 on fragments taken immediately above the dorsal lip and fragments of 

 presumptive ventral ectoderm showed oxygen uptake of the same order 

 of magnitude in both. According to determinations by J. Brachet (1936), 

 however, CO^ production is about 85 per cent higher in pieces from the 

 dorsal lip than in ventral pieces; oxygen uptake per milligram of nitro- 

 gen is 35 to 40 per cent higher in the dorsal than in the ventral pieces; 

 and the respiratory quotient is 1.06 in the dorsal, as compared with 0.76 

 in ventral pieces. The higher CO2 production in the dorsal lip results in 

 part from a higher absolute rate of metabolism and in part from the 

 higher respiratory quotient. 



Simultaneous determination of oxygen uptake of the two sides of single 

 intact eggs and embryos showed the dorsal side averaging 47 per cent 

 higher than the ventral in gastrulae of the frog {Rana sylvatica) .^^ With 

 orientation of the embryos in the capillary so that the dorsal lip was 

 symmetrically placed in relation to the two sides of the apparatus, no 

 significant difference in oxygen uptake appeared. The authors suggest 

 that the earlier failure by Waddington, Needham, and Brachet (1936) to 

 discover a difference in respiration of dorsal and ventral piece probably re- 

 sulted from use of pieces taken from above the dorsal lip rather than from 

 the dorsal lip itself. They also point out that alteration of respiratory 

 rate after isolation may be concerned in determinations on isolated pieces. 

 In unfertilized eggs of R. pipiens they found no consistent difference in 

 oxygen uptake between apical and basal hemispheres. If there is any 

 actual difference, it is probably very slight until activation occurs on fer- 

 tilization or by other means, and it may decrease when the egg remains 

 for some time without fertilization. 



Determinations of oxygen uptake, respiratory quotient, ammonia pro- 

 duction, anaerobic and aerobic glycolysis in very small fragments of dorsal 

 and ventral regions of amphibian embryos of various species with the 

 Cartesian diver used as an ultramicrorespirometer show no consistent dif- 

 ferences in oxygen uptake, a higher respiratory quotient dorsally (about 

 i), as found by Brachet, anaerobic glycolysis of dorsal pieces about three 



3^ J. Brachet and Shapiro, 1938. Eggs and embryos were introduced singly into capillary 

 tubes with lumen about equal to, or slightly larger than, their diameter, and each end of the 

 tube was connected with a manometer. 



