OCTOBEB 4, 1907] 



SCIENCE 



427 



C3H,^ 



(CnHjn — lOj): 



N, 



PO OH, 



o/ 



C,H,N(CH3)30H. 



The eliolin can apparently not be utilized 

 for the synthesis of nucleins, but the other 

 constituent is able not only to furnish the 

 phosphoric acid skeleton of the nucleic acid 

 molecule, but also the carbohydrates. The 

 fatty acid could be rendered available for 

 this purpose by oxidation, and we shall see 

 indeed that phenomena of oxidation are 

 the prerequisite of the synthesis of nu- 

 cleins. If the lecithin of the egg is utilized 

 for this synthesis it is obvious that the 

 lecithin molecule must first undergo a 

 cleavage, whereby it is freed from the 

 eholin group. The question as to whether 

 or not lecithin is the source of the phos- 

 phates and possibly some other constituents 

 of the nucleic acid group can not be decided 

 until the synthesis of the nucleic acid has 

 been accomplished. 



Some further data concerning the syn- 

 thesis of nucleic acid in the egg can be 

 obtained. The fertilized egg can not de- 

 velop or increase the number of its nuclei 

 unless an ample supply of free oxygen is 

 present. Twelve years ago I showed that 

 if all the oxygen is withdrawn from the 

 egg, no nuclear, and no cell division is pos- 

 sible, and no increase in its mass of nuclein 

 occurs. The same effect is accomplished if 

 we inhibit the oxidations in the egg 

 through the addition of KCN. The latter, 

 or possibly the HON formed by hydro- 

 lytic dissociation, inhibit the oxidations in 

 the egg. The addition of ^ c.c. of a 1/20 

 per cent, solution of KCN to 50 c.c. of 

 sea-water is sufficient to bring to a complete 

 standstill the effect of the fertilization in 

 the egg of the sea-urchin, without other- 

 wise injuring the egg, provided the latter 

 does not remain too long in the absence of 

 oxygen or the presence of KCN. As soon 

 as oxygen is again admitted to the egg 

 which has been deprived of it, the synthesis 



of nuclein and the segmentation begin 

 again ; the same occurs when the eggs are 

 brought back from the cyanide sea-water 

 to normal sea-water, provided they are 

 sufficiently aired. It is therefore obvious 

 that the nuclein synthesis depends abso- 

 lutely upon a process of oxidation. 



By way of digression I may mention that 

 this role of oxidation in cell division should 

 induce teachers of physiology to discon- 

 tinue the antiquated statement that the 

 sole object of oxidation in living cells is 

 the production of heat. Oxidations occur 

 in plants and animals which do not need 

 to keep up a constant temperature. But 

 in all these animals a synthesis of nuclein 

 and cell divisions occurs. 



We can further show that aside from 

 the process of oxidation, still other proc- 

 esses are originated or accelerated through 

 the entrance of the spermatozoon into the 

 egg and that these processes occur even in 

 the absence of oxygen. This follows from 

 the difference in the resistance of the fertil- 

 ized and the unfertilized eggs towards lack 

 of oxygen. Fertilized eggs suffer much 

 more quickly from lack of oxygen or from 

 KCN than unfertilized eggs. Eggs were 

 fertilized and a few minutes later put into 

 sea-water free from oxygen, in which they 

 remained twenty-four hours at a tempera- 

 ture of about 15° C. No segTiientation or 

 increase in nuclei occurred in the eggs 

 while they were without oxygen. At the 

 end of the twenty-four hours, air was ad- 

 mitted- and segmentation began; many 

 eggs, however, segmented abnormally and 

 none developed beyond the blastula stage. 

 Simultaneously the same experiment was 

 made with the unfertilized eggs of the same 

 female. When after twenty-four hours 

 air was admitted and sperm added, all the 

 eggs developed into normal plutei. The 

 same experiment can be made more easily 

 and strikingly by adding KCN to the sea- 

 ■water. These facts show that lack of 



