Bichat shows, in his researches on life and death, how the black and carbonized blood disturbs the functions of the brain and acts like a narcotic poison, causing the heart finally to cease its throbbings. These miasms and poisons floated about the enclosure where there was not the least sign of vegetable organism to absorb and convert them. As they passed into the systems of the prisoners they became the cause of disease, decrepitude, and death. X. Vitiated air is one of the most subtile and powerful of poisons, and it seems to affect soldiers more than any other class of persons, and its consequences have been commented upon by most of the military writers,--from Xenophon among the Greeks, Vegetius among the Romans, down to those of the present time. Cavalry horses have been observed to suffer deterioration and death from the same cause. Ague and fever, states Dr. Johnson, "two of the most prominent features of the malarious influences, are as a drop of water in the ocean when compared with the other, but less obtrusive, but more dangerous maladies that silently disorganize the vital structure of the human fabric under the influence of this deleterious and invisible poison." One fourth of the sailors of the English navy are sent home invalided every year, and one tenth of them die from the effects of foul air of their cabins. "Two thirds of the pulmonary diseases which desolate England are induced by this cause." Baudelocque long ago pointed out its influences in the etiology of scrofula. It is really the same influence observed by Magendie, and not contradicted to the present day, that putrid blood, brain, bile, or pus, when laid on flesh wounds, produce in animals, after a longer or shorter interval, vomiting, languor, and death. The same results and phenomena are observed in the inspiration of bad air; the most terrible forms of fever arise from the overcrowding of people in confined and limited spaces. Most of the zymotic diseases enter by the lungs, which are the principal absorbing agents. The breathing in of foul air, loaded with perceptible and putrid animal and vegetable emanations, gives rise to those zymotici, the ideas of which originated with Hippocrates, and to which the distinguished Liebig has since given form and prominence. Not only is animal life disturbed and destroyed, but we observe that vegetables even are affected by the same or similar causes; that they are extremely susceptible of impurities in the air, and that the rapidity and vigorous appearance of their growth are affected whenever there is very slight modification in the healthy proportions of the atmosphere. Again, we see how seeds, when placed in elementary oxygen, germinate with extreme rapidity, and soon decay, thus indicating how the presence of nitrogen in the natural air restrains the force of the other element. XI.