[31] It would thus appear that carbonic acid, in its most concentrated form, may kill by exciting a spasmodic action, in which the epiglottis is closed, and the entrance of air into the lungs altogether prevented. In a diluted form, it may destroy by its specific influence upon the blood, which would seem to be of a highly sedative character. Death produced by such an agent is probably attended with little or no suffering. The younger Berthollet destroyed his life by inclosing himself in an atmosphere of this description; and on commencing his fatal experiment, he registered all the successive feelings he experienced, which were such as would have been occasioned by a narcotic:--a pause, and then an almost illegible word occurred: it is presumed that the pen dropped from his hand,--and he was no more. It may perhaps appear extraordinary to the reader of the "RESEARCHES," that although they were published not more than eighteen months after the appearance of his "Essays on Heat and Light," no allusion is made in them either to his theory or to his new nomenclature. In relating his experiments upon Respiration, he employs the conventional language of the schools, and the word "_phos-oxygen_" does not once occur in the volume. This is fully explained in a communication made by him to Mr. Nicholson, and which was printed in his Journal a short time after the publication of his Essays in the West Country Contributions; in which he says,--"As facts have occurred to me with regard to the decomposition of bodies, which I had supposed to contain light, without any luminous appearance, I beg to be considered as a _sceptic_ with respect _to my own_ particular theory of the combinations of light, until I shall have satisfactorily explained those anomalies by fresh experiments. On account of this scepticism, and for other reasons, I shall in future use the common nomenclature; excepting that, as my discoveries concerning the gaseous oxide would render it highly improper to call a principle, which in one of its combinations is capable of being absorbed by venous blood, and of increasing the powers of life, _azote_,--I shall name it, with Dr. Pearson, Chaptal, and others, NITROGENE; and the _gaseous oxide of azote_ I shall call NITROUS OXIDE." The same feeling is expressed at the conclusion of his Third Research.--"It would be easy to form theories referring the action of blood impregnated with _nitrous oxide_, to its power of supplying the nervous and muscular fibre with such proportions of condensed nitrogen, oxygen, light, or ethereal fluid, as enabled them more rapidly to pass through those changes which constitute their life; but we are unacquainted with the composition of dead organized matter; and new instruments of experiment, and new modes of research, must be found, before we can ascertain even our capabilities of discovering the laws of life."