SECT. 8] CARBOHYDRATE METABOLISM 1013 



related to the process of bone formation, which, as von Baer estab- 

 lished, proceeds at this time. Its calcium and phosphorus require- 

 ments have been studied in detail, and will be found discussed in 

 Section 13-2, but very little attention has been paid to its need for osseo- 

 mucoid. Even less is known about osseomucoid than about ovomu- 

 coid, but we may make a calculation which is suggestive. The amount 

 of osseomucoid in fresh bone has not been accurately ascertained, 

 and no estimation method has ever been devised for it. Hawk & 

 Gies obtained 7 gm. of pure osseomucoid from 1 700 gm. of fresh 

 bone (0-04 per cent.), but they were not trying to work quantita- 

 tively. On the other hand, we know from the analyses of von Bibra; 

 Schrodt; Wildt; Morguhs; and Weiske that the organic matter in 

 bone amounts to about 33 per cent, of the fresh weight. The nearest 

 approximation to the amount of osseomucoid would seem to be one- 

 tenth of the organic substance. According to Tangl, the weight of 

 the bones in the chick at hatching is 1-446 gm. dry weight, i.e. 

 3-616 gm. wet weight. This leads to an organic content of 1-205 gm. 

 and about 120 mgm. of osseomucoid. Assuming its proportion of 

 glucose to be 33 per cent., we get an equivalent in glucose of 40 mgm. 

 Tangl's value for the weight of connecti\'e tissues at hatching is 

 0-405 gm. dry weight, or, assuming a water-content of 75 per cent., 

 1-615 gm. wet weight. The mucoprotein would here amount to 

 about 60 mgm., and the corresponding glucose to 20 mgm. There 

 would thus be 60 mgm. of mucoprotein-glucose present in the 

 finished embryo. Since just under 200 mgm. of ovomucoid glucose 

 have disappeared since the loth day, it is evident that the muco- 

 protein of the raw material has some other goal besides the muco- 

 protein of the completed article, but the temporal correlation holds 

 good, for, just as during the period of importance of connective tissue 

 there was catabolism of ovomucoid, so here in the period of growth 

 of bone there is a similar effect. 



The closely related ovomucoid of reptile eggs has been investi- 

 gated by Takahashi on those of Thalassochelys corticata. During de- 

 velopment the percentage of ovomucoid in the organic matter of the 

 egg-white varies from 33 to 17 per cent. The ovomucoid is attacked 

 by amylase and yields 6-2 per cent, glucose (notably less than avian 

 ovomucoid). Takahashi was inclined to think, on the basis of rather 

 few analyses, that the elementary composition of the substance 

 changed as the embryo developed. 



