SECT. 9] PROTEIN METABOLISM mi 



96-9 mgm. (5825 to 5728) per 100 eggs, and reason will be given 

 later for supposing that this is largely, perhaps preponderantly, due 

 to the combustion of carbohydrate. 



9-10. Protein Metabolism in Teleostean Ontogeny 



Gortner applied the same methods to the study of the protein 

 metabolism of the brook-trout's egg {Savelinus fontinalis) . This was 

 more satisfactory than his study of the salamander's tgg, among 

 other reasons because he pursued its development to completion, 

 i.e. until the larvae had lost their yolk-sacs, and were ready to take 

 food. The figures for total nitrogen were as follows: 



Gortner attached no importance to the gain of 20 mgm. recorded 

 for the second sample, or to the loss of 30 mgm. recorded for the 

 third. He preferred to average the first three readings, and to say 

 that, before hatching, 400 eggs of the trout have a constant figure 

 for total nitrogen at 874-8 mgm. The difference between this figure 

 and that first obtained after hatching, namely, 51 mgm., he 

 put down to the loss of the egg-membranes, but it is more than 

 probable that the greater part of it consisted of nitrogenous end 

 products which had been retained in the eggs, and were now 

 liberated. Certainly the consumption of protein after hatching during 

 the last third of development was considerable. We can make a rough 

 calculation to see how much of the 51 mgm. was egg-membrane 

 protein, for Kronfeld & Scheminzki noted that the membranes of 

 the trout egg were 8-25 per cent, of the total dry weight, i.e. 

 582 mgm. in this case at hatching, or, taking its nitrogen content 

 at 14-5 per cent, and assuming that the membrane is at least 50 per 

 cent, keratin, 42 mgm. of nitrogen. But this is a high estimate, for 

 it is known that the egg-membranes of fishes become diaphanous and 



