350 ANIMAL PHYSIOLOGY. 
It is now known that there are several kinds of peptones, a 
disclosure for which we were not unprepared, considering our 
imperfect knowledge of proteids in general; but there have 
been other developments which, on the supposition that the 
peptone of the alimentary canal is freely absorbed as such, are 
startling enough. It has been shown that these peptones, at 
least as prepared by artificial digestion, have three effects when 
injected in quantity into the blood of an animal: They produce 
narcosis; they retard or prevent coagulation of the blood; they 
lower blood-pressure. The first effect may be dependent in 
whole or in part on the third. 
But, inasmuch as the venom of poisonous reptiles, according 
to recent investigations, is essentially proteid in nature, it is 
plain that we must exercise great caution in drawing conclu- 
sions in regard to the physiological effects of proteid bodies, so 
long as our knowledge of their exact chemical composition is 
so imperfect. That the chemist can make out no great differ- 
ence between peptones prepared in the laboratory and the di- 
gestive tract, or even between these and snake-venom, though 
they have such different effects when injected into the blood, 
is clear proof of how much we have yet to learn of these 
bodies. 
But we introduce these considerations here rather to show 
that it is by no means likely that any great quantity of pep- 
tones passes into the blood as such at any one time. It has 
been recently suggested that peptone is converted into globulin 
in the liver. But what proof is there of this? And already 
we have credited the liver with a large share of work. 
For a considerable period it has been customary to use the 
terms endosmosis and diffusion in connection with the func- 
tions of the alimentary canal, and especially the intestinal tract, 
as if this thin-walled but complicated organ, or rather collec- 
tion of organs, were little more, so far as absorption is con- 
cerned, than a moist membrane, leaving the process of the re- * 
moval of digested food products to be explained almost wholly 
on physical principles. 
From such views we dissent. We believe they are opposed 
to what we know of living tissue everywhere, and are not sup- 
ported by the special facts of digestion. When certain foreign 
bodies (as purgatives) are introduced into the blood or the ali- 
mentary canal, that diffusion takes place, according to physical” 
laws, may indicate the manner in which the intestine can act; 
but even admitting that under such circumstances physical 
