I2I2 METABOLISM OF LIPOIDS, STEROLS, [pt. iii 



embryo, minute in amount as they are during the first lo days, must 

 be almost wholly combined in the lipoid molecule, and only towards 

 the end of development, when the fat content is beginning to rise 

 sharply, does the coefficient rise too, showing an accumulation of 

 neutral fat. Presumably by shortly after hatching the ratio would 

 approach one of the lower levels seen in the table given above. 

 Cahn's figures for the ratio are plotted in Fig. 383. 

 JavilHer & Allaire later suggested the use of the following coefficients : 



Purine phosphorus 

 J Lipoid phosphorus 



Total phosphorus — (lipoid phosphorus + purine phosphorus) 



Total phosphorus 

 which latter is equivalent to 



Inorganic phosphorus + water-soluble organic phosphorus 



Total phosphorus 



X 100. 



It is instructive, however, to compare the data of Javillier & 

 Allaire, and of Javillier, Cremieu 



Level of guinea-pig 



& Hinglais, for various adult 

 tissues, with the data at our dis- 

 posal for the foetal tissues of the 

 chick and the undeveloped egg, 

 more especially as Javillier & 

 Cremieu have investigated in 

 this way the tissues of various 

 invertebrates, and Javillier, Al- 

 laire & Rousseau the tissues of 

 the whole white mouse from 

 birth to 40 days of post-natal life. 

 JavilHer & Cremieu, in compar- 

 ing the invertebrate tissues with 

 those of mammals, suggested 

 using the total phosphorus minus 

 the inorganic phosphorus as the 

 denominator, instead of the true 

 total phosphorus, a procedure 

 which they hoped would make 

 a better basis of comparison. This non-calcification phosphorus they 



Days 



Fig- 383- 



