422 Dr. R. D. Thomson on the Digestion of 



tion when dissolved in water, and therefore corresponds with 

 that variety of soluble starch which has frequently been de- 

 scribed by chemical writers. It appeared a point of some im- 

 portance to ascertain whether the transition of starch into 

 dextrin takes place at once in the stomach, or whether the 

 change commences before the food is swallowed. I accord- 

 ingly prepared a quantity of porridge by boiling it for upwards 

 of half an hour with distilled water, and on filtering it I ob- 

 tained distinct evidence of the presence of dextrin in the fil- 

 tered liquid. It may perhaps therefore be legitimate to in- 

 fer that one of the important purposes to be acquired by 

 cooking starch is to facilitate its conversion into soluble dex- 

 trin, and that other form of soluble starch already described ; 

 and hence the importance of the boiling being continued for a 

 considerable space of time, when some of the harder species 

 of amylaceous food, as rice, sago, tapioca, are used as arti- 

 cles of diet, and especially when they are administered to the 

 delicate stomachs of the sick. 



The soluble starch was separated in the manner already 

 detailed, and was found to possess the following constitution 

 when subjected to organic analysis : — 



7*29 grains gave 9-86 COg 

 7-11 ... 9-54 CO2 



13-93 ... 7-97 HO 



7-29 ... 4-05 HO 



7-11 ... 4.-03 HO 



The result of these analyses per cent, is as follows : — 



This composition does not agree with that of starch, except 

 with wheat starch, in the carbon before that substance has 

 been dried; but according to the analyses of Prout, the hy- 

 drogen in wheat starch is greater in amount than in the pre- 

 sent case. The carbon in the substance under consideration 

 agrees with that of sugar of starch, but the hydrogen is much 

 inferior; and the three experiments detailed agree so closely 

 in reference to the hydrogen, that there can be little doubt of 

 the accuracy of the results, more especially as the last ana- 

 lysis was made with oxide of copper and chlorate of potash, 

 and the matter subjected to analysis appeared to be completely 

 burned. The substance appears to have possessed some in- 

 termediate characters between those of sugar and starch. 



Sugar in the Blood. — The preceding results show that a 



