608 ORGANS OF GENERATION. 



tilization, development and artificial parthogenesis of the eggs of sea 

 animals have already been discussed in connection with the physico- 

 chemical processes and action of ions (Chapter II). Here it will be 

 sufficient to call attention to the fact that LOEB believes that a synthesis 

 of the nuclear substance, i.e., of nucleoproteins from the constituents 

 of the yolk, is the means of stimulating development, and that oxidation 

 processes direct the proper path of the nuclear syntheses. The setting 

 free of the nuclear syntheses and these oxidation processes also depend 

 upon a change in the peripheral layers of the egg, which is in general 

 followed by a formation of a membrane, and this latter seems to be brought 

 about by zytolytically acting bodies and the liquefaction of a lipoid. 

 The impulse for the development of the egg is according to this assump- 

 tion the liquefaction of a lipoid on the surface of the egg, and from this 

 follows another assumption that the head of the spermatozoa contain 

 a lipoid-liquefying substance. 



The placenta has recently been the subject of several investigations. 

 This tissue contains a protein which coagulates at 60-65 C. (BOTTAZZI 

 and DELFINO) whose relation to the nucleoprotein, found by others, is 

 not clear. The protein found by SAVARE contained 0.45 per cent phos- 

 phorus. The nucleic acid studied by KiKKOJi, 1 which is very similar to 

 the thymus nucleic acid, originates from this nucleoprotein. Glycogen 

 occurs regularly in the placenta and MOSCATI believes the human pla- 

 centa contains 5 p. m. glycogen. After removal the glycogen diminishes, 

 and after 24 hours it has disappeared. According to LOCHHEAD and 

 CRAMER 2 the quantity of glycogen in the placenta is not increased by 

 food, rich in carbohydrate. In the foetus (rabbits) the above authors 

 found that the placenta is a storage organ for glycogen until the 

 second half of the gestation period, when the liver begins to functionate 

 in this direction. From this time on the quantity of glycogen in the 

 placenta diminishes. 



Enzymes of various kinds, proteolytic as well as lipolytic (mono- 

 butyrase), amylases and oxidases have been found in the placenta (AscoLi, 

 RAINERI, BERGELL and LIEPMANN, SAVARE 3 ) . In the edges of the placenta 

 of the bitch and of cats an orange -colored, crystalline pigment (bilirubin) 

 and a green, amorphous pigment, whose relation to biliverdin is not 

 clear, have been found. 4 



1 Bottazzi and Delfino, Centralbl. f. Physiol., 18, 114; Savare, Hofmeister's Beitrage, 

 11; Kikkoji, Zetischr. f. physiol. Chem., 53. 



2 Moscati, Zeitschr. f. physiol. Chem., 53; Lochhead and Cramer, Proc. Roy. Soc., 

 80 B. (1908). 



3 Ascoli, Centralbl. f. Physiol., 16; Raineri, Bioch. Centralbl., 4, 428; Bergell and 

 Liepmann, Munch, med. Wochenschr., 1905; Savare, Hofmeister's Beitrage, 9. 



4 See Etti, Maly's Jahresber., 2, 287, and Preyer, Die Blutkristalle, Jena, 1871. 



