The experiments of which I have given the detail, exemplify phenomena which do not indeed take place in the ordinary process of inspiration, and therefore I allow that no very rigorous induction can be drawn from them, with respect to the passage of deleterious substances into the mass of the blood; nevertheless it appears to me, that they very much confirm the probability of such fact, which besides is demonstrated by many of the preceding remarks. I shall conclude, then, that such passage is real. In fact, we have seen 1st, That the sole transmission of the black blood into the arteries, will not account for the infinitely various phenomena exemplified in the different sorts of asphyxiæ; 2dly, That the simple contact of the deleterious substance with the nerves of the lungs, can by no means be the cause of a death so rapid as that which is occasioned by these accidents; 3dly, That, therefore, we are forced as it were to suspect the passage of the poison itself into the blood; 4thly, That a number of considerations are in favour of such suspicion, and thus that the fact is proved both directly and indirectly.[109]
This principle being once established, a variety of results must flow from it. Of the first of these, of the mode of action, namely, which the deleterious substance must exercise upon the different organs, I shall say nothing, having nothing to offer but conjecture.
I shall accordingly content myself with inquiring what system it is which is particularly influenced by these substances, when mingled with the blood.--Now, 1st, This system appears to be the nervous one, and that portion of it especially, which presides over the parts of the animal life, the organic functions being only secondarily affected; 2dly, Of all the nervous system, the brain is that part which is the most affected; 3dly, Under this relation Monsieur Pinel appears to me to have been right, in placing some of the asphyxiæ (those for instance which are occasioned by the presence of a deleterious substance) among the neuroses. On this head the following considerations should leave us little doubt.
1st, In all the asphyxiæ, when the presence of a deleterious substance cannot be doubted, the symptoms consist of two general and opposite sets of phenomena, of spasm and torpor. Of two workmen who had come up out of the sewer of the street St. André des Ares, the one sat himself down upon a bulk, and fell into a state of asphyxia; the other with irregular convulsive movements, proceeded as far as the rue Battoir, and then fell down asphyxiated. The Sieur Verville, in consequence of inhaling the breath of a man who was lying in a state of asphyxia from the vapour of lead, fell down suddenly, and in a short time became convulsed. The vapour of charcoal intoxicates, as it is said. I have seen animals asphyxiated with other gases, and perishing with a stiffness, such as could be produced only by the most violent spasm. The centre of all these symptoms, and the organ from which they emanate, undoubtedly is the brain, and they depend upon its irritation or compression.