SECT. 8] CARBOHYDRATE METABOLISM 1007 



8-3. Ovomucoid and Combined Glucose 



It is easy to calculate the amount of carbohydrate not present as 

 glycogen or free glucose outside the embryo, for every day during 

 development. This is graphically shown in Fig. 269. But such a cal- 

 culation suffers from the fact that the non-glycogen sugar is assumed 

 to be all free, which cannot be the case, but this error does not reach 

 grave dimensions till the last 5 days of incubation, and as the correction 

 would tend then to increase the free glucose outside the embryo it 

 would tend also to decrease the ovomucoid glucose outside the embryo. 

 We may therefore allow for the fact that the descent of this curve in 

 Fig. 269 at the end of development is rather more precipitous than the 

 graph makes it. 



This curve, which, for want of a better name, we may call the 

 "ovomucoid" curve, shows some interesting relationships. In the 

 first place, its initial value, namely 133 mgm., is in fair agreement 

 with the independent data of Komori, which have already been 

 referred to (see p. 268). Komori prepared ovomucoid from fresh 

 hen's eggs, obtaining from 333 gm. of albumen 4-8 gm. of ovomucoid. 

 The processes were carried out as quantitatively as possible in order 

 to get an idea of the concentration of the substance. This would 

 mean 140 mgm. of ovomucoid glucose present at the beginning of 

 development, which agrees very well with the 133 mgm. calculated 

 from Needham's estimations by difference. This result gives us some 

 confidence in interpreting the changes occurring in this fraction as 

 changes in ovomucoid content. 



What are these changes? As can be seen from Fig. 269, the ovo- 

 mucoid curve falls until the 5th day is reached, after which point 

 it rises to a peak on the loth day, thence to fall steadily till the time 

 of hatching. The initial fall is of great interest in view of Komori's 

 experiments in which he showed that Miiller & Masayama's egg 

 "amylase" can very efficiently split off the sugar from ovomucoid. 

 We may suppose that the heating of the egg at the beginning of 

 incubation would set the enzyme in action, like the mechanism already 

 suggested which controls yolk viscosity during the ist week (see 

 p. 836). By the 20th day there are at most half-a-dozen milHgrams 

 of ovomucoid left. All the carbohydrate outside the embryo at that 

 time can be accounted for by glycogen and free glucose. From the 

 fact that this peaked effect is found so markedly in the ovomucoid 



