16 BULLETIN 507, U. S. DEPARTMENT OF AGRICULTURE. . 



Summary of digestion experiments uith egg yolk in a simple mixed diet. 



Experi- 

 ment No. 



Suliject. 



Protein. 



Fat. 



Carbohy- 

 drates. 



Ash. 



214 



D. o. a 



Per cent. 



81.3 

 84.1 

 8.5.6 

 75.1 

 80.1 



Per cent. 

 92.0 

 91.4 

 91.7 

 91.0 

 90.9 

 92.1 



Per cent. 

 96.0 

 96.1 

 96.9 

 97.5 

 94.5 

 95.9 



Per cent. 

 64.5 



215 



216.. 



K. L. S 



O.E.S 



57.7 

 65.4 



217 



R.F.T 



62.2 



302 



303 



H. F. B 



O.E.S 



42.3 

 53.7 





Average.. . 







81.6 



91.5 



96.2 



57.6 









It may be noted from the recorded data of these experiments that 

 the average amounts of protem, fat, and carbohydrate eaten daily 

 were 56, 85, and 326 grams, of which 81.6, 91.5, and 96.2 per cent 

 were digested, respectively. The reported digestibihty of 91.5 per 

 cent for the total fat of the diet is increased to 93.8 per cent for the egg- 

 yolk fat by making allowance for metabohc products and any undi- 

 gested portion of the small amount of fat the basal ration supplied. 

 Inasmuch as the egg-yolk fat comprised 98 per cent of all the fat 

 supphed by the diet, this derived value should very closely approxi- 

 mate the true digestibility of egg-yolk fat. 



In the course of the analytical work it was observed that the ether 

 extracts of both the blancmange and the feces of the experimental 

 periods were of a very dark-orange color, somewhat more intense in 

 the case of the feces. This discoloration can probably be attributed 

 to coloring matter extracted from the egg yolk. 



FISH FAT. 



Though fish fat or oil (for it is liquid at ordinary room temperature) 

 is not a cuhnary or table fat in our temperate regions, nevertheless, 

 as it occurs in fish flesh, it forms a not inconsiderable part of the total 

 fat of the diet. This is particularly the case in localities where such 

 fish as mackerel, butterfish, salmon, shad, etc., are eaten in quantity. 

 Except in the case of cod-liver oil, which is a special product used in 

 invaUd dietetics chiefly because of the medicinal properties attributed 

 to it, experimental studies of food uses of fish fat or oil are apparently 

 few in number. 



Atwater/ in a study of haddock compared with beef, reports that 

 the fish fat was 91 per cent digested. Some years later Milner,^ in 

 experiments with four young men, found that the digestibility of the 

 fat of a lean fish (cod) was practically the same as that of a fat fish 

 (canned salmon), the values being 97.4 per cent and 97 per cent, 

 respectively. 



Since fish oil suitable for food purposes was not found on the market 

 and it was not practicable to prepare it in the laboratory, fish con- 

 taining a fairly high percentage of fat was used instead in the experi- 



1 Ztschr. Biol., 24 (1888), pp. 16-28. 



2 Connecticut Storrs Sta. Itpt. 1905, pp. 116-142. 



