96 CYCLOSES, CHOLESTEROL AND CHOLIC ACID 



form of fine white acicular crystals by the addition of ether to an 

 alcoholic solution. It has a sweet taste, but being neither actually nor 

 potentially an aldehyde or ketone, it does not reduce metallic oxides 

 in alkaline solution, and hence, of course, does not reduce Fehling's 

 solution. It is precipitated from aqueous solutions by lead acetate 

 containing an excess of lead oxide ("basic lead acetate"). 



Inosite may be recognized by the above peculiarities, by its melting- 

 point (225), and by the following characteristic reactions: 



Gallois' Reaction. A drop of inosite solution is mixed with a drop of 

 mercuric nitrate solution and heat gently applied until the water has 

 evaporated. A yellow color at first appears which changes on further 

 heating to a deep red. This color disappears on cooling, and reappears 

 on reheating. 



Scherer's Reaction. A few crystals of inosite are dissolved in a drop 

 or two of nitric acid of specific gravity 1.2, and an equal volume of ten 

 per cent, calcium chloride solution is added and the same volume of a 

 one per cent, solution of platinic chloride. This mixture is evaporated 

 to dryness and the residue heated, when a rose-red color appears, which 

 disappears on cooling, and reappears with a bluish nuance on reheating. 



Inosite is found in small amounts in normal urine, and the amount 

 increases in certain pathological conditions, particularly in diabetes 

 insipidus and in Bright's disease. The administration of inosite in 

 unusual amounts by mouth gives rise to transient diarrhoea and to an 

 increase in the Creatinine output in the urine, a fact which, in the light 

 of considerations which will be detailed in subsequent chapters, may 

 possibly indicate increased destruction of tissue-substances. Only a 

 very small proportion of the inosite administered by mouth is excreted 

 in the urine, the remainder being oxidized and eliminated in the form 

 of products which are apparently indistinguishable from those of 

 ordinary carbohydrate-combustion. In phloridzinized dogs the excre- 

 tion of d-glucose in the urine, already a maximum, is increased by 

 administration of inosite, and if the ^additional output of glucose be 

 added to the inosite which is excreted unchanged in the urine, the sum 

 is approximately equal to the inosite administered. Under these 

 circumstances, therefore, the ring-formation appears to undergo a 

 simple splitting with the partial transformation of inosite, molecule 

 for molecule, into glucose. 



Cycloses other than i-inosite occur in vegetable tissues but with one 

 exception have not as yet been identified among the constituents of 

 animal tissues. The exception is Scyllite which is found in the tissues 

 of the bony (Teleost) fishes. It gives Scherer's reaction and is optically 

 inactive, but it may be distinguished from i-inosite by its very high 

 melting-point; 380 as contrasted with 225. 



In vegetable tissues occur 1-inosite in the form of the methyl ester 

 in quebracho bark, d-1-inosite or racemic inosite (a mixture of the d- and 

 1-varieties) in the leaves of mistletoe, and d-inosite in the rosin and 

 needles of conifers, in senna leaves and in India-rubber. 



