882 



GENERAL METABOLISM 



[PT. Ill 



H Allanfcoic(Kamei) 

 nAmniotic( ^ ) 

 ® Allantoic 

 (Rske&,Bqyden) 



& Riddle found that the fluid filling the subgerminal cavity in the 

 pigeon's egg would hardly form a coagulum when heated, and evi- 

 dently contained only a little protein. 



Closely associated with the water metabolism of the egg is the 

 origin of the amniotic and allantoic liquids. Kamei has studied their 

 increase in volume (see Fig. 227). The allantoic fluid shows at first 

 a fairly regular rise and by the 

 middle of development reaches 



6 c.c, after which it probably 

 falls. These 6 c.c. represent 

 about 15 per cent, of all the 

 water in the egg, i.e. that per- 

 centage has been required to 

 assist in the excretion of from 



7 mgm. (Fiske & Boyden) to 

 3I mgm. (Needham) of uric 

 acid (see p. 1 092) . The reabsorp- 

 tion of water from the allantois 

 must begin very soon after the 

 mid-point of development, for 

 by the 12th day its uric acid 

 content is increasing while its 

 volume is remaining steady 

 or diminishing. The amniotic 

 liquid, on the other hand, reaches what is practically its maximum 

 by the loth day and does not fall until the final desiccation of the egg 

 before hatching begins. 



The specific gravity of the amniotic liquid rises to a maximum 

 on the 14th day but that of the allantoic liquid rises throughout 

 development, as follows : 



Amniotic Allantoic 



1-0062 1-0070 



1-0630 1-0147 

 1-0400 1-0205 



especially turtles, contain white^, and 

 Agassiz gave a description of the histology of their yolk after laying, 

 which has been interpreted by Bartelmez & Riddle as indicating 



0) 2 

 E 



Fig. 227. 



Day 

 9 



17 



The eggs of reptiles, 



^ Deraniyagala describes the white as at first viscid and later quite mobile and limpid. 

 This is precisely the opposite to what happens in avian eggs (see Figs. 207 and 215) but 

 would be expected from the considerable water-intake (see p. 898, Table 105). 



