Mitchell on the Penetrativeness of Fluids. 109 



atmosphere of carbonic acid, where in less than ten minutes the 

 inflation caused it to burst. On repetition of this experiment and 

 examination before fracture, a very large quantity of carbonic acid 

 gas was discovered to have entered the intestine. Crop, bladder, 

 &c. &c. of recently killed animals produced exactly similar results. 

 Perhaps the following experiment will be esteemed even more satis- 

 factory. Carefully removed from the chest of a snapper, (Testudo 

 serpentaria^) its lung was partially inflated with common air, and 

 confined there by a ligature on the tracheal tube. Exposed in this 

 state to an atmosphere of carbonic acid, or nitrous oxide, it became 

 very soon fully inflated by the gas to which exposed, as subse- 

 quently proved by chemical examination. Less than half an hour 

 of exposure sufficed for the full inflation of the lung, which was 

 removed only when it threatened to burst. Containing a portion of 

 nitrogen, it was left exposed all night to an atmosphere of oxygen, 

 yet scarcely enough entered to signify its presence ; in quantity 

 superior to that which is held in atmospheric air. A taper appeared 

 in it somewhat brighter than before its immersion. 



In a subsequent experiment, the two lungs of a snapper having 

 been extracted, were inflated respectively, with common air, and 

 carbonic acid gas. So prepared, each lung was surrounded by a 

 bell-glass containing an atmosphere of the other gas, so that common 

 air surrounded the carbonic acid, et vice versa. That lung which 

 contained common air soon burst by the infiltration of carbonic acid, 

 while the other collapsed by its escape. 



In concluding the series of experiments on the question of fact, 

 some were made on living animals. A quantity of solution of acetate 

 of lead having been thrown into the peritoneal cavity of a young cat, 

 sulphuretted hydrogen was discharged from the pipe of the gene- 

 rating retort, directly into the rectum. In four minutes the poi- 

 sonous gas killed the animal, giving to it, because of enormously 

 dilated pupils, a very wild aspect. Instantly on its death, which 

 was itself an affair of a moment, the peritoneal coat of the intestines, 

 and the walls of the cavity in contact with them, were found lined 

 with a metallic-looking precipitate, adherent to the surface, and sus- 

 ceptible of removal by nitric acid, moderately diluted. It was the 

 characteristic precipitate of sulphuretted hydrogen when acting on 

 lead. When, in another experiment, the abdominal cavity was almost 

 instantly opened, only the intestines and stomach presented the 

 bronzed aspect ; the peritoneum of other parts, and the bladder, 

 appeared of their natural colour, thus proving that the gas had in- 

 filtrated, and not passed through any rent or fracture, an event 



