DIGESTION OF FOOD. 849 
previous ones, points in the direction of the control of this 
process by the nervous system. But if the views we hold of 
the absolute dependence, especially in the higher animals, of 
all vital processes on the nervous system are correct, it fol- 
lows, as a matter of course, that absorption in living tissues, 
which we do not regard as wholly explicable by any physical 
process, but as bound up with all the functions of cell-life, 
must be dependent on that connection we are endeavoring to 
emphasize between one tissue and another, and especially the 
dominating tissue, the nervous system. 
There are two points that are very far from being deter- 
mined: the one the fate of the products of digestion; the other 
the exact limit to which digestion is carried. How much— 
e. g., of proteid matter—does actually undergo conversion into 
peptone; how much is converted into leucin and tyrosin; or, 
again, what proportion of the albuminous matters are dealt with 
as such by the intestine without conversion into peptone at all, 
either as soluble proteid or in the form of solid particles ? 
1. It is generally believed that soluble sugars are absorbed, 
usually after conversion into maltose or glucose, by the capil- 
laries of the stomach and intestine. 
2. There is some positive evidence of the presence of fats, 
soaps, and sugars in unusual amount after a meal in the portal 
vein, which implies removal from the intestinal contents by 
the capillaries, though, so far as experiment goes, the fat is 
chiefly in the form of soaps. 
‘Certain experiments have been made by ligating the pyloric 
end of the stomach, by introducing a cannula into the thoracic 
duct, so as to continually remove its contents, etc. But we are 
surprised that serious conclusions should have been drawn under 
such circumstances, seeing that the natural conditions are so 
altered. What we wish to get at in physiology is the normal 
function of parts, and not the possible results after our inter- 
ference. Under such circumstances the phenomena may have 
a suggestive but certainly can not have a conclusive value. 
It is a very striking fact that little peptone (none, according 
to some observers) can be detected even in the portal blood. 
True it is, the circulation is rapid and constant, and a small 
quantity might escape detection, yet a considerable amount be 
removed from the intestine in the space of a few hours by the 
capillaries alone. Peptone is not found in the contents of the 
thoracic duct. 
Recent investigations have thrown a new light on peptone. 
