ORIGIN OF SUGAR IN THE ANIMAL ECONOMY. 99 
plastic aliments in the production of sugar. But when we 
reflect, that the transformation of fat into sugar cannot be 
explained in the present state of our knowledge ; that, on 
the other hand, the presence, in the economy, of an abundant 
respiratory aliment like fat, may in some degree shelter the 
sugar existing already, or formed by the tissues from the 
influence of the oxygen, we soon see that fresh researches 
are necessary to solve this problem. 
Third Question. — Is the Saccharine Matter formed by the 
Digestive Action , in the Liver, or during the Circulation ? 
First Experiment. — A full-grown dog was fed for eight days 
upon bread, moistened with fat broth. After two days of 
complete abstinence, he had one kilogramme of bread and 
some water given to him. Three hours after this repast, the 
abdomen having been opened and the blood of the various 
vessels collected separately, I ascertained the quantity of 
sugar in these products, and I found in the blood of the vena 
porta 0*322 percent, of sugar; in the blood of the hepatic 
veins 0*327 ; in the blood of the vena cava inferior 0* 103 ; 
and in that of the carotid artery 0*052 per cent. The mat- 
ters contained in the stomach and intestines contained a 
good deal of sugar. 
I made three similar experiments, but their general results 
did not vary. 
Seco7id Experiment. — A large full-grown dog was subjected 
to the action of chloroform on the third day of absolute 
abstinence, and the blood was collected from the vena porta, 
the super-hepatic veins, the vena cava inferior, and the crural 
artery. Analysis gave the following results: — 0 025 parts of 
sugar in 100 of the blood of the vena porta, 0*049 per cent, 
in the blood of the hepatic veins, 0*042 in the blood of the 
vena cava inferior, and 0 023 in the blood of the crural 
artery. 
Third Experiment. — A dog was left without food for eight 
days and then killed. The examination of the blood of 
different vessels gave the following results : — 0*022 per cent, 
of sugar in the blood of the hepatic veins, and merely traces 
in the vena cava inferior. The blood of the vena porta 
contained no sugar. In another dog, which had been kept 
fasting for four days, no sugar was found in the vena porta, 
whereas some was found in the hepatic veins. 
Fourth Experiment. — A dog, fed for eight days upon cooked 
meat, then after an abstinence of 36 hours, having received a 
copious meal of cooked meat, was killed during the course of 
the digestion. The blood of the vena porta contained no 
sugar. The blood of the hepatic veins contained 0*340 per 
