SECT. 12] CYCLOSES, PHOSPHORUS, SULPHUR 



1231 



inositol, instead of a hexaphosphate, but at present there is no reason 

 for supposing that such compounds exist in the body. 



In order to get some insight into the precursor of inositol, Needham 

 injected a series of unincubated eggs with various substances, phytic 

 acid, hexamethylenetetramine (to test the hypothesis of Posternak 

 who suggested that inositol might arise from the condensation of six 

 molecules of formaldehyde) and glucose. Tests showed subsequently 



600q 



500- 



+ 250 mg. glucose 



250 mg. glucose 



300- 



■ = embryo 

 O = remainder 



+ 725 mg. glucose 



Normal 



Normal and + 125 mg. glucose 



f 250 mg. lieKamethylene-tetramina 



— r- 



20 



Fig. 396. 



the presence of formaldehyde in the egg-interior after injection of 

 hexamethylenetetramine, but neither the eggs which had received 

 phytic acid nor those which had received hexamethylenetetramine 

 could be got to develop normally. Doubtless the highest concentration 

 compatible with normal development could have been found by 

 further searching, but, in view of the positive results obtained with 

 glucose, this was not undertaken. For, as Fig. 396 shows, injection of 

 glucose markedly increased the inositol content of the embryo, though 

 not of the rest of the egg. It would therefore seem likely that the 

 synthesis of inositol from glucose only takes place within the embryo. 

 The existence of this synthesis in the developing embryo agreed with 



