320 ABSORPTION. 



of Bernard) by poisoning a pigeon with woorara drawn by a fistula from the stomach of 

 a living dog. If we recognize the absorption of this poison simply by its effects upon the 

 system, it must be assumed that, during digestion, it cannot be absorbed by the mucous 

 membrane of the stomach and small intestine, notwithstanding that it is exceedingly 

 soluble. 



It has also been shown that liquids which immediately disorganize the tissues, such as 

 concentrated nitric or sulphuric acid, cannot be absorbed. Another important peculiar- 

 ity in absorption has been demonstrated by Mialhe, who has shown that solutions which 

 readily coagulate the albumen of the circulating fluids are absorbed very slowly. This 

 is explained on the supposition that there is a coagulation of the albuminous fluids with 

 which the absorbing membrane is permeated, which interferes with the passage of 

 liquids. These substances are nevertheless taken up by the blood-vessels, though rather 

 slowly. 



The modifications which are due simply to the physical conditions of liquids to be 

 absorbed are chiefly manifested out of the body and will be considered in connection with 

 the subject of endosmosis. 



Influence of the Condition of the Blood and of the Vessels on Absorption. After loss 

 of blood or deterioration of the nutritive fluid from prolonged abstinence, absorption gen- 

 erally takes place with great activity. This is well known, both as regards the entrance 

 of water and alimentary substances and the absorption of medicines. It was at one time 

 quite a common practice to bleed before administering certain remedies, in order to pro- 

 duce their more speedy action upon the system. 



The rapidity of the circulation has an important influence upon absorption. "We have 

 already shown, in treating of the action of the blood-vessels on absorption, that this pro- 

 cess may be impeded or even arrested by the ligation of important vessels. It has been 

 evident, also, that absorption is generally active in proportion to the vascularity of differ- 

 ent parts. During the process of intestinal absorption, the increase in the activity of the 

 circulation in the mucous membrane is very marked and undoubtedly has an influence 

 upon the rapidity with which the products of digestion are taken up. 



Influence of the Nervous System on Absorption. Experiments upon the influence of 

 the nervous system on absorption are still very imperfect. It is certain that this process, 

 especially in the stomach, is subject to variations, which can hardly be dependent upon 

 any thing but nervous action. Water and other liquids, which usually are readily ab- 

 sorbed from the stomach, are sometimes retained for a time, and are afterward rejected 

 in nearly the condition in which they were taken. It is probable, however, that the most 

 important influences thus exerted by the nervous system are effected through the circu- 

 lation. The recent experiments of Bernard and others upon the sympathetic system of 

 nerves and its connection with the muscular coats of the small arteries, by the action of 

 which the supply of blood in different parts is regulated, point out a line of experimenta- 

 tion which would probably throw much light upon some of the important variations in 

 absorption. When it is remembered that the small arteries may become so contracted 

 under the influence of the sympathetic system that their caliber is almost obliterated, 

 of course retarding to a corresponding degree the capillary and venous circulation in the 

 parts, and, again, that, through the sympathetic nerves, the same vessels may be so 

 dilated as to admit to a particular part three or four times as much blood as it ordinarily 

 receives, it becomes apparent that absorption may be profoundly affected through this 

 system of nerves. 



As far as the influence of the cerebro-spinal system is concerned, it has been ascer- 

 tained that, while section of some of the nerves distributed to the alimentary canal will 

 slightly retard the absorption of poisonous substances, it is never entirely arrested. Lon- 

 get found that the operation of strychnine injected into the stomach of a dog in which 



