1232 



METABOLISM OF LIPOIDS, STEROLS, [pt. iii 



the conclusions of Greenwald & Weiss, who studied the composition of 

 the urine in dogs after injection of inositol into the circulation, and with 

 those of Needham, Smith & Winter, who studied the behaviour of the 

 free inositol of the body in insulin convulsions. No information is as 

 yet available concerning the way in which the inositol ring is formed 

 from glucose, although, as is well known, rings can be formed by the 

 body, e.g. kynurenic acid. The hen's egg would be a good material to 

 choose in a study directed towards ascertaining the method of syn- 

 thesis of the cyclose molecule. 



12-7. Sulphur Metabolism of the Avian Egg 



The presence of sulphur in the hen's egg is familiar on account of 

 the deposit of ferrous sulphide at the boundary of yolk and white 

 after long boiling (Tinkler & 

 Soar).i The first work which 

 might be included under this 

 heading was that of Lieber- 

 mann, who estimated the sul- 

 phur in the feathers during the 

 last week of incubation, but his 

 method was very questionable, 

 and, as his figures show no 

 definite gradation or constancy, 

 little attention need be given 

 to them. Hopkins' isolation of 

 glutathione in 1921 made it 

 essential to re-open the ques- 

 tion of sulphur metabolism in 

 the egg, and he himself ob- 

 served that in the fresh egg 

 the nitroprusside reaction was 





OWhole embryo.wetl 1^ 



" .dry J "'■'■^y 

 O » " , as sulphur wet(Cahn) 



© >. » ,wet| 

 ® Brain, wet Waoi 

 e Muscle wet, ) 



Days 



10 



15 



Fig- 397- 



quite negative, although the blastoderm and germinal area of a 

 3 days' embryo gave a brilliantly positive result. This was confirmed 

 by Tunnicliffe. Some years later Murray estimated the glutathione 

 present in the chick embryo at diflferent stages, using Tunnicliffe's 

 method. It was found to be nearly all in the reduced form, and the 

 amounts obtained increased, as was to be expected, with the increase 



^ And the tarnishing of silver by egg-yolk was known to Pliny: 

 luteo". 



'nigrescit ovi indurati 



