VARIATIONS AND MODIFICATIONS OF ABSORPTION. 



319 



animals, showed that, although the intestinal mucous membrane became of a deep black, 

 this could easily be removed by a stream of water, and no carbonaceous particles could 

 be discovered in the mesenteric veins, the lacteals, or the mesenteric glands. When the 

 carbon is used in the form of lamp-black, the particles are very minute and rounded, and 

 they do not present the sharp points and edges which sometimes enable the grains of 

 pulverized charcoal to penetrate the vessels mechanically. 



FIG. 95. Epithelium from the duodenum of a rab- 

 bit, two hours after having been fed with melt- 

 ed butter. (Fuhke.) 



FIG. 96. Villi, filled with fat. from the small in- 

 testine of an executed criminal, one hour after 

 death. (Funke.) 



Variations and Modifications of Absorption. 



Very little is known concerning the variations in lacteal or lymphatic absorption ; 

 but, in absorption by blood-vessels, important modifications occur, due, on the one hand, 

 to different conditions of the fluids to be absorbed, and, on the other, to differences in the 

 constitution of the blood and in the conditions of the vessels. 



The different conditions of the fluids to be absorbed apparently do not always have 

 the same influence in physiological absorption as in endosmotic experiments made out of 

 the body. Saccharine solutions of different densities confined in distinct portions of the 

 intestinal canal of a living animal do not present any marked variations in the rapidity 

 of their absorption, and they are taken up by the blood, even when their density is 

 greater than that of the blood-plasma. Solutions of nitrate of potash and sulphate of 

 soda of greater density than the serum, which would, therefore, attract the endosmotic 

 current in an endosmometer, are readily taken up by the blood-vessels in a living animal. 

 Indeed, nearly all soluble substances, whatever be the density of their solutions, may be 

 taken up by the various absorbing surfaces during life. The woorara poison and most of 

 the venoms are remarkable exceptions to this rule. In a series of very interesting 

 experiments upon the absorption of woorara, Bernard has shown that this curious poison, 

 which is absorbed so readily from wounds or when introduced under the skin, generally 

 produces no effect when introduced into the stomach, the small intestine, or the urinary 

 bladder. This result, however, is not invariable, for poisonous effects are produced when 

 woorara is introduced into the stomach of a fasting animal. This peculiarity in the 

 absorption of many of the animal poisons has long been observed ; and it is well known 

 that the flesh of animals poisoned with woorara can be eaten with impunity. It is 

 curious, however, to see an animal carrying in the stomach without danger a fluid which 

 would produce death if introduced under the skin ; and the explanation of this is not 

 readily apparent. The poison is not neutralized by the digestive fluids, for woorara 

 digested for a long time in gastric juice, or taken from the stomach of a dog, is found to 

 possess all its toxic properties, as we have frequently shown (repeating the experiment 



