276 THE PHYSIOLOGY OF REPRODUCTION 



in circumscribed masses throughout the body, and the cells of the so- 

 called hibernating gland. All these cells have the appearance of 

 glandular cells in which numerous lipoid globules are deposited. It 

 is very probable that these various groups of tissues are functionally 

 correlated in so far as the metabolism of cholesterin and the associated 

 lipoids is concerned, so that changes or disturbances in the cholesterin 

 metabolism will be reflected in these various tissues. But from this 

 to an identity of function is a far cry. 



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 reducing substance glucosamine and 

 therefore belong to the group of glycoproteins. Hammarsten l 

 isolated a substance, called by him Pseudomucin, which did not 

 coagulate on heating and was not precipitated by acetic acid. On 

 hydrolysis it yielded thirty per cent, glucosamine. Pfannenstiel 2 

 isolated from ovarian colloid another mucoid substance, Pseudomucin 

 /?, 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. 3 



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 gm., half of this being the weight of the 

 white of the egg, while the yolk weighs 12-18 gm. and the shell 

 5-8 gm. 



The egg - shell contains chiefly calcium 4 carbonate. During 

 development the egg-shell loses inorganic substances, especially 

 calcium, to the amount of 0'15 gm. This goes to the building up of the 

 structures of the developing embryo. 5 In some species the shell is 



1 Hammarsten, " Metalbumin und Paralbumin," Zeitsch. f. physiol. Ckem., 

 vol. vi., 1882. 



2 Pfannenstiel, "Uber die Pseudomucine der cystischen Ovariengeschwulste," 

 Arch. f. Giptcekologie, vol. xxxviii. 



3 For further details concerning the chemical pathology of the ovaries see 

 Wells' Chemical Pathology, 3rd Edition, 1918. 



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

 Egg before and after Incubation," Jour, of Physiol., vol. i., 1878. 



5 Tangl, "Untersuchungen iiber die Beteiligung der Eischale am Stoffwechsel 

 des Einhalts wahrend der Bebriitung," Pfliige) J 8 Arch., vol. cxxi., 1908. 



