BIOCHEMISTRY OF THE SEXUAL ORGANS 279 



the name " percaglobulin." ^ It is rich in sulphur, and is pre- 

 cipitated by weak hydrochloric acid. It has an astringent 

 taste, and possesses the remarkable property of forming pre- 

 cipitates with some glucoproteins such as ovomucoid, and with 

 polysaccharides such as glycogen and starch. This substance 

 could not be found when the eggs were mature, and does not 

 appear to be present in the ovaries of other fishes. 



Very important and interesting results have been obtained 

 by systematic chemical examinations of the muscles and ovaries 

 of the salmon ^ and of the herring ' at different seasons. 

 Extensive chemical changes take place in these animals during 

 the period of their reproductive activity. The reproductive 

 organs develop at the expense of the muscles, which diminish 

 in weight. This is best seen in the case of the salmon, since 

 this animal does not take any nourishment during its passage 

 up the rivers. In the case of the herring the conditions are not 

 quite so simple, because the herring feeds until spawning occurs, 

 although less food is taken in the later months. 



In the case of the salmon, then, the ovaries are built up from 

 material contained in the muscle. The most marked change in 

 the muscle during that period is a loss of fat, with which the 

 muscles are loaded when the salmon leaves the sea. The protein 

 constituents of the muscle also diminish, but not to the same 

 extent as the fat. There is, further, a disappearance of the 

 inorganic phosphates of the muscle. From these substances 

 the ovaries build up their essential constituents — the phospho- 

 protein ichthulin and the phosphorised fats. The source of the 

 choUne which is contained in the phosphorised fats is not yet 

 clear. This formation by the ovaries of phosphorised fats out 

 of fats and inorganic phosphates points to the important function 

 which these organic phosphorus compounds have to fulfil in 

 the developing organism (see above). 



Not all the fat which disappears from the muscles reappears 



' Mijrner, " Percaglobulin ein oharakteristischer Eiweisskbrper aus dem 

 Ovarium des Barsches," Zeitschrift fiir physiolog. Chemie, vol. xl. 



" Miescher, Histochemische und physiologiache Arbeiten. Noel Paton and 

 others, " Report of Investigations on the Life-History of the Salmon in Fresh 

 Water," Report to the Fishery Board for Scotland, 1898. 



" Milroy, " Changes in the Chemical Composition of the Herring during 

 the Reproductive Period," Biochemical Journal, vol. iii., 1908, p. 366, 



