636 ORGANS OF GENERATION. 



284.5 grams potash, 235.6-329.3 soda, 17.4-29.0 lime, 17-31.7 magnesia, 

 4.4-5.5 iron oxide, 238.4-285.6 chlorine, 31.6-48.3 phosphoric acid (P 2 O 5 ), 

 13.2-26.3 sulphuric acid, 2.8-20.4 silicic acid, and 96.7-116.0 grams carbon 

 dioxide. Traces of fluorine have also been found (NicKLES 1 ). The 

 white of egg contains, as compared with the yolk, a greater amount of 

 chlorine and alkalies and a smaller amount of lime, phosphoric acid, and 

 iron. 



The Shell-membrane and the Egg-shell. The shell-membrane con- 

 sists, as above stated (page 112), of a keratin substance. The shell con- 

 tains very little organic substance, 36-65 p. m. The principal mass, more 

 than 900 p. m., consists of calcium carbonate; besides this there are very 

 small amounts of magnesium carbonate and earthy phosphates. 



The diverse coloring of birds' eggs is due to several different coloring-matters. 

 Among these we find a red or reddish-brown pigment called " oorodein " by 

 SoRBY, 2 which is perhaps identical with hsematoporphyrin. The green or blue 

 coloring-matter, SORBY'S oocyan, seems, according to LIEBERMANN 3 and KRUKEN- 

 BERG, 4 to be partly biliverdin and partly a blue derivative of the bile-pigments. 



The eggs of birds have a space at their blunt end filled with gas; this 

 gas contains on an average 18.0-19.9 per cent oxygen (HuFNER 5 ). 



The weight of a hen's egg varies between 40-60 grams and may some- 

 times reach 70 grams. The shell and shell-membrane together, when 

 carefully cleaned, but still in the moist state, weigh 5-8 grams. The 

 yolk weighs 12-18 and the white 23-34 grams, or about double. The 

 entire egg contains 2.8-7.5, or average 4.6, milligrams of iron oxide, and 

 the quantity of iron can be increased by food rich in iron (HARTUNG 6 ) . 



The white of the egg of cartilaginous and bony fishes contains only traces of 

 true albumin, but consists, at least in many fishes, of mucin substance; and the 

 cover of the frog's egg also consists, according to GIACOSA, of mucin. The eggs 

 of the river-perch contain, HAMMARSTEN 7 claims, mucin in the envelope in the 

 unripe state and only mucinogen in the ripe state. The crystalline formations 

 (yolk-spherules, or dotterpldttchen) which have been observed in the egg of the 

 tortoise, frog, ray, shark, and other fishes, and which are described by VALEN- 

 CIENNES and FREMY under the names emydin, ichthin, ichthidin, and ichthulin, 

 seem, as above stated in connection with ichthulin, to consist mainly of phos- 

 phoglycoproteins. The klupeovin obtained by HUGOUNENQ 8 from the herrings' 

 eggs and from which he obtained the three so-called hexone bases and abundant 



1 Compt. Rend., 43. 



2 Cited from Krukenberg, Verb. d. phys.-chem. Gessellsch. in Wiirzburg, 17. 

 8 Ber. d. deutsch. chem. Gesellsch., 11. 



1. c. 



6 Arch. f. (Anat. u). Physiol., 1892. 

 Zeitschr. f. Biol., 43. 



7 Giacosa, Zeitschr. f. physiol. Chem., 7; Hammarsten, Skand. Arch. f. Physiol., 17. 

 8 Valenciennes and Fr&ny. cited from Hoppe-Seyler, Physiol. Chem., p. 77; 

 Hugounenq, Bull. soc. chim. (3), 33, and Compt. Rend., 143. 



