1234 METABOLISM OF LIPOIDS, STEROLS, [pt. m 



seems to be in or associated with the embryonic body. Cahn calcu- 

 lated from his figures the following ratio: 



which ran as follows : 



Apparently therefore, the total organic sulphur in the embryo grows 

 fairly closely parallel with the total nitrogen. This simple fact may 

 involve so many contributory processes that a trite allocation of 

 significance to it is hardly warranted. 



Although strictly speaking out of place here, the work of Thompson 

 & Voegtlin on the rat embryo may be mentioned. As it is the only 

 work on the sulphur metabolism of the mammalian embryo, it can 

 best be taken now. Thompson & Voegtlin estimated the amounts of 

 glutathione by the Tunnicliffe method in rats of different ages, ob- 

 taining the following results : 



Weights Milligrams glutathione 



in grams per 100 gm. wet weight 

 Embryos ... ... 0-07- o-8o 60 



1-04- 1-97 58 



2-32- 2-95 54 



^^ -- 3-89- 4-67 44 



Newly-born ... ... 4"65- 4-95 36 



Nursing 23-00- 26-00 32 



Weaned ... ... 30-00- 50-00 31 



Adult 137-00-170-00 23 



Thus it has been shown both for the chick and for the rat that the 

 concentration of glutathione in the tissues declines with age both 

 during the embryonic and post-embryonic periods. 



Targonski, in his work on the allantoic liquid, measured the 

 amount of total sulphur in it. Its amount and concentration, judging 

 from his few analyses, do not seem to be changing in any very definite 

 way, but he calculated the total sulphur/total nitrogen ratio, and 

 found it to be slowly rising, i.e. 0-067 ^^ the 14th day, 0-095 on the 

 1 6th and 0-105 on the i8th. It was thus moving in the opposite 

 direction from the total phosphorus/total nitrogen ratio. He could 

 only conclude that towards the end of incubation the breakdown of 



