264 THE PHYSIOLOGY OF REPRODUCTION 



strong nitric acid and sulphuric acid they give a blue colour. 

 Their solutions in alcohol, ether, or chloroform are further 

 characterised by the absorption-spectrum, 1 which shows two 

 bands in the blue part of the spectrum (between the lines F 

 and G). 



Observations concerning the chemistry of human ovaries have 

 been made chiefly in certain pathological conditions of these 

 organs. Various protein substances have been isolated from 

 the fluid contents of ovarian cysts. In the case of cysts due 

 to a dilatation of the Graafian follicles the contents were found 

 to be identical with other serous liquids. From cystic tumours 

 of the ovaries, the contents of which may be either watery or 

 gelatinous, a number of protein compounds have been isolated, 

 which, on hydrolysis, all yield a considerable quantity of a re- 

 ducing substance glucosamine and therefore belong to the 

 group of glycoproteins. Hammarsten 2 isolated a substance, 

 called by him Pseudomucin, which did not coagulate on heating 

 and was not precipitated by acetic acid. On hydrolysis it yielded 

 30 per cent, glucosamine. Pfannenstiel 3 isolated from ovarian 

 colloid another mucoid substance, Pseudomucin /3, a gelatinous 

 mass which was insoluble in acetic acid and water, but was 

 dissolved by dilute alkali. These substances are formed by the 

 activity of the cells lining the cysts. 



Birds 



Our knowledge of the chemistry of the ovum is derived 

 almost entirely from investigations on the hen's egg. The 

 average weight of an egg is 40-60 grm., half of this being the 

 weight of the white of the egg, while the yolk weighs 12-18 

 grm. and the shell 5-8 grm. 



The egg-shell contains chiefly calcium carbonate. During 

 development the egg-shell loses calcium, which goes to the 

 building up of the structures of the developing embryo. 4 In 



1 Thudichum, " Uber das Lutein und die Spektren gelbgefarbter organ- 

 ischer Substanzen," Centralblatt f. d. med. Wissenschaft, 1869, vol. vii. 



2 Hammarsten, " Metalbumin und Paralbumin," Zeitschr. f. physiol. 

 Chemie, vol. vi., 1882. 



3 Pfannenstiel, " Uber die Pseudomucine der cvstischen Ovarienge- 

 schwiilste," Arch. f. Gyncekologie, vol. xxxviii. 



4 Vaughan, "Estimation of Lime in the Shell and in the Interior of the 

 Egg before and after Incubation," Journal of Physiology, vol. i., 1878. 



