It appears, however, from some experiments performed by Professor Orfila on occasion of a judicial case to be mentioned presently, that all the forms of acetic acid will prove injurious and even fatal to dogs, if given in sufficient quantity and prevented from being discharged by vomiting. An ounce of pyroligneous vinegar, administered to dogs of middle size, and retained in the stomach by a ligature on the gullet, produces efforts to vomit, evident suffering, prostration of strength, and death in five, seven, or nine hours. An ounce of concentrated acetic acid occasioned death in one hour and a quarter; and four or five ounces of common vinegar proved fatal in ten or fifteen hours. These experiments would make it appear that acetic acid is scarcely less active as an irritant poison than even the mineral acids.[381] They are in some measure confirmed by the prior experiments of Schubarth; who operated, however, with an impure reddish-brown pyroligneous acid, and was led to ascribe its energy to the presence of some empyreumatic oil, because he found, as was already remarked, that a pure acid of equal strength appeared almost inert. From half an ounce to an ounce of the impure acid given to dogs, caused fruitless efforts to vomit, sometimes free vomiting, occasionally great flow of tears, always weakness in the hind-legs, and feeble, irregular pulse, and death either in two days without any new symptom of consequence, or more rapid death in four or five hours, with previous convulsions, and sometimes insensibility.[382] These experiments were made with an acid which neutralized 50 grains of carbonate of lime per ounce, consequently contained at least 50 grains of concentrated acid, or about a tenth of its weight. To these observations it may be added, that according to the experiments of Hébréart, a small quantity of acetic acid dropped into the windpipe, produces hissing respiration, rattling in the throat, and death in three days from true croup.[383] In all the preceding experiments distinct evidence was obtained in the dead body of the irritant action of the poison. The stomach contained brownish-black blood, the villous coat was blackish, and the subjacent cellular tissue injected with black blood; sometimes there was an appearance of erosion on the surface of the villous coat; and in the instance of the concentrated acid perforations were found. In the experiments of Hébréart the lining membrane of the windpipe was covered with a fibrinous pseudo-membrane, exactly as after croup.