FLESH AND ITS PEEPAEATIOXS. 



349 



232. EGGS must be regarded as a complete food, as the organism of the young- 

 chick is developed from them. The yolk contains a characteristic proteid body 

 vitellin ( 249), and an albuminate in the envelopes of the yellow yolk spheres 

 nuclein, from the white yolk ; fats in the yellow yolk (palmitin, olein), cholesterin, 

 much lecithin ; and as its decomposition-product, glycerin-phosphoric acid (/rape- 

 sugar, pigments (lutein), and a body containing iron and related to haemoglobin ; 

 lastly, salts qualitatively the same as in blood quantitatively as in the blood-cor- 

 puscles and gases. The chief constituent of the white of egg is egg-albumin 

 ( 249), together with a small amount of palmitin and olein partly saponified with 

 soda ; grape-sugar, extractives ; lastly salts, qualitatively resembling those of blood, 

 but quantitatively like those of serum, and a trace of fluorine. Eelatively more of the 

 nitrogenous constituents than of the fatty constituents of eggs are absorbed (Rubner). 



[The shell is composed chiefly of mineral matter (91 per cent, of calcic carbonate, 6 per cent, 

 of calcic phosphate, and 3 per cent, of organic matter. A hen's egg weighs about If oz., of 

 which the shell forms about ^. Note the amount of fats in the yolk.] 



Composition : 



233. FLESH AND ITS PREPARATIONS. Flesh, in the form in which it 

 is eaten, contains, in addition to the muscle-substance proper, more or less of the 

 elements of fat, connective- and elastic-tissue mixed with it ( 293). The following 

 results refer to flesh freed as much as possible from those constituents. The chief 

 proteid constituent of the contractile muscular substance is myosin ; serum-albumin 

 occurs in the fluid of the fibres, in the lymph and blood of muscle. The fats are 

 for the most part derived from the interfascicular fat-cells, while lecithin and chole- 

 sterin come from the nerves of the muscles ; the gelatin is derived from the connec- 

 tive-tissue of the perimysium, perineurium, and the walls of blood-vessels and 

 tendons. The red colour of the flesh is due to the haemoglobin present in the 

 sarcous substance, but in some muscles, e.g., the heart, there is a special pigment, 

 myohsematin (MacMunn). Elastin occurs in the sarcolemma, neurilemma, and in 

 the elastic fibres of the perimysium and walls of the vessels ; the small amount of 

 keratin is derived from the endothelium of the vessels. The chief muscular sub- 

 stance, the result of the retrogressive metabolism of the sarcous substance, is hreatin 

 ( 0'05 per cent.) ; hreatinin, the inconstant inosinic acid, then lactic, or rather 

 sarcolactic acid ( 293). Further, taurin, sarkin, xanthin, uric acid, carnin, inosit 

 (most abundant in the muscles of drunkards), urea (0*1 per cent.) dextrin (in horse 

 and rabbit, not constant) ; grape-sugar, but this is very probably derived post-mortem 

 from glycogen (0*43 per cent), which occurs in considerable amount in foetal 

 muscles ; lastly volatile fatty acids. Amongst the salts, potash and phosphoric 

 acid compounds are most abundant ; magnesium phosphate exceeds calcium phos- 

 phate in amount. [The composition varies somewhat even in different muscles of 

 the same animal.] 



In 100 parts Flesh there are, according to Schlossberger and v. Bibra 



