Dr, Mitchell on the Occurrence of Sugar in the Animal Econoimj. 93 



fermentation, as soon as possible, established in an infusion. When the 

 process was completed, it was distilled and redistilled till I obtained what 

 I now present to you. 



There is another application of the fermentation test — I refer to the 

 production of the Torula Cerevisi, which can be readily and positively 

 recognised by the microscope, when the examining eye is one accustomed 

 to the use of the instrument. 



In quantitative analyses, I have estimated the sugar by the amount of 

 carbonic acid given off, reckoning one cubic inch of gas as equivalent to 

 one grain of grape sugar, or by more accurate calculation, 100 C. I. of 

 CO2 correspond to 106.4 of sugar. Or if the COo be estimated by weight, 

 one grain of the gas will be found equal to 2J grains of sugar. 



One thing of importance has to be attended to in searching for sugar 

 in the blood, viz. that sugar is destroyed in, and disappears from, the 

 blood, after being drawn with great rapidity, so that it becomes necessary 

 to act on the serum as soon as ever the coagulation is sufficiently com- 

 plete. In order to prevent this destruction it is only requisite to coagulate 

 the blood as it escapes from the vessel by alcohol or acetate of lead, after 

 which the sugar will remain unchanged for a considerable period. 



As regards the variety of sugar which exists in the animal economy, 

 we may conclude that it is neither sugar of milk nor cane sugar. It 

 cannot be the sugar of cane, for it is rendered brown by the action of 

 potash, and reduces the salts of copper ; nor, since it ferments readily, 

 can it be the sugar of milk. There remains, therefore, the grape sugar, 

 and of this the sugar of the liver presents the chemical characters. The 

 optical experiments of M. Biot show the sugar of diabetes to be identical 

 with the sugar produced from starch. It is possible, therefore, that this 

 animal sugar may possess certain differences in its properties, although it 

 agrees in all essentials with the grape sugar. Indeed, there is some 

 reason for believing that this will by and by be established. 



I shall now, gentlemen, recapitulate the conclusions, which, to my 

 mind, seem the necessary deductions from the foregoing considerations: — 

 It would appear, in the first place — 1st. That sugar exists uniformly and 

 normally in the blood of the heart ; I say the blood of the heart, because 

 it will be shown afterwards that it may have all but disappeared before 

 arriving at the superficial veins of the body, where bleeding is usually 

 practised. 



2dly. That its presence there is independent of diet, 



3dly. That the sugar is found specially concentrated in the liver of 

 animals. 



4thly. That there is reason to believe that it is formed in the liver, 

 which thus becomes at once the seat and origin of the sugar. 



5thly. That in the use of a saccharine diet, sugar enters the circula- 

 tion directly as sugar. 



And lastly, that these considerations oblige us to reject the doctrine 

 that animals do not create any immediate principle, but simply destroy 



