1252 METABOLISM OF LIPOIDS, STEROLS, [pt. iii 



decline per lOO gm. dry weight, so does the former. It was made 

 up as follows : 



" Unsaponifiable X and Y" Cholesterol 



Hours from f ■ — ''■ — ^ , ^ ^ 



fertilisation % dry weight % ether extract % dry weight % ether extract 

 o 1-5 7-0 1-8 8-7 



40 



7-4 

 7-5 



1-65 

 1-4 



12-13. Lipoids and Sterols in Mammalian Development 



A certain number of quantitative determinations of lipoid phos- 

 phorus in individual tissues have been made, but these will be reserved 

 for consideration in Section 23. Baumann & Holly found 560 mgm. 

 per cent, phosphatides in a 20th-day rabbit embryo and 650 in a 

 29th-day one, also corresponding values of 240 and 230 mgm. per 

 cent, for cholesterol. Vignes found 205 mgm. per cent, in whole rats 

 (maternal) and 654 mgm. per cent, in their embryos. If we pass to 

 nucleoprotein phosphorus we meet immediately with Masing's work. 

 In 191 1 this investigator estimated the nucleoprotein phosphorus in 

 rabbit embryos at different stages of development, but as he used no 

 accurate time scale it is impossible to plot his data. All that can be 

 done is to reproduce the table in which he summarised his results : 



Table 177. 



Embryos \X.o\\ cm. long, from the ist half of gestation 



Embryos 21*5 gm. weight, about 4th week 



Embryos a little older than the last lot 



Embryos i or 2 days before birth 



Fully developed embryos 



Newly born rabbits 



Rabbits 1 1 days after birth 



Liver from beginning of 4th week 



Liver from a little later stage ... 



Livers from embryos i to 2 days before birth 



Livers of new-born rabbits 



Livers of rabbits 1 1 days old ... 



Livers of rabbits 22 days old ... 



Adult livers 



Nucleoprotein phosphorus 



associated with 350 mgm. 



of total nitrogen 



20-3 



17-4 



14-7 



13-0 



I2*0 



II-7 

 1 1-9 



2i2-8 

 20'4 



180 



I7-0 

 i6-o 



I2-0 



IO-7 



The nucleoprotein phosphorus thus decreases relatively to the total 

 nitrogen (i.e. approximately to the dry weight), and correspondingly 

 the nucleoplasmatic raUo decreases. This is in agreement with what 

 has already been said in the Section on purine metaboHsm. 



This is all that we know about the phosphorus metabohsm of the 



