84 ABSORPTION AND EXHALATION L.ECT. IV. 



into the fold for the purpose of admitting a brass tube, 

 which was so fastened by means of thread that the substance 

 to be introduced should not touch the bleeding edge of the 

 opening. This being done, a ligature was passed under the 

 vein receiving the blood from the fold. The ligature was 

 tightened ; and, in order that the circulation should not be 

 stopped, the vein was opened to allow the escape of the re- 

 turning blood. Then, by means of a glass funnel and the 

 brass tube, some concentrated hydrocyanic acid was intro- 

 duced into the fold, and the tube then closed. The venous 

 blood returning from the intestine was immediately collected, 

 and found to contain hydrocyanic acid ; but the animal pre- 

 sented no symptoms of poisoning, notwithstanding that the 

 nerves and lymphatics remained untouched. 



In another experiment Pannizza, instead of tying and 

 opening the venous trunk where the small veins discharged 

 themselves, merely compressed it at the moment the hydro- 

 cyanic acid was introduced. There was no symptoms of 

 poisoning ; but shortly after the removal of the pressure, 

 symptoms of poisoning appeared ; and, the vein being 

 opened, the contained blood was found to be impregnated 

 with the acid. 



Lastly, in a third experiment, Panizz.a quickly, but care- 

 fully, removed, all the lymphatic vessels and nerves of the 

 intestinal fold; and, hydrocyanic acid being pour.ed in, 

 speedily destroyed the animal, provided that the vein was 

 untouched. Venous absorption is thus proved by the most 

 accurate experiments. 



In some works on physiology it is stated that the fact of 

 substances being detected in the urine, a few minutes after 

 their introduction into the stomach, is opposed to the opinion, 

 that absorption takes place by means of the blood-vessels. 

 But this objection soon falls to the ground, when we con- 

 sider the rapidity of the circulation of the blood., 



