precise experiments recently made by MM. Jules Reiset, Muntz, and Aubin, on the proportion of carbonic acid in the atmosphere, which go to show that the proportion of this gas in the air of Paris is no more considerable than in the country, we have a right to affirm that positively no danger to the public health exists from this source.
The truth is, that most of the accidents which happen in burial-places must be attributed only to confined carbonic acid. These accidents are, moreover, much less numerous than is supposed. Different authors do not report more than twelve or fifteen cases, and the theory that cemeteries are centers of infection has been built upon this small basis. Such accidents have been attributed to "pestilential emanations, to certain subtile and deleterious gases, to unhealthy miasms," etc. In reality, the accidents noted have been caused by the carbonic acid which has settled in the pits or vaults by virtue of its superior specific gravity. The same happens much more frequently than in cemeteries, in lime-kilns, marl-pits, some cellars, fermenting vats, everywhere, in short, that carbonic acid is liable to accumulate within a limited space.
The absence of any facts relative to other gases than carbonic acid that might be disengaged in the course of cadaverous decomposition ought to have made those who are so sure of the dangerous character of cemeteries more circumspect; notwithstanding there are no such facts, these persons, besides magnifying the dangerous consequences of the liberation of carbonic acid, speak also of the no less fearful dangers which result from the generation of "certain gases and of certain volatile products." Only two gases have been found to be present to an appreciable extent in the confined air of mortuary vaults, or in the atmosphere immediately surrounding a body in decomposition—as, for instance, within the inclosure of a leaden coffin. These two gases are poisonous when breathed in a certain quantity; they are ammonia and sulphuretted hydrogen, forming, when they combine, sulphohydrate of ammonia. The most delicate reagents disclose no trace of these gases in the free air, nor even in the atmosphere of the cemeteries of Paris, although such tests often, when applied in the same manner, indicate their presence in water-closets, sinks, cellars, and sewers. In the absence of ammonia and sulphuretted hydrogen, we might (though no one has yet done so) imagine the presence of the ptomaïnes, those alkaloids of dead bodies recently discovered by Professor Selmi. We anticipate this accusation, by observing that the presence of ptomaïnes in the open air has never been detected. It has been proved that they are not always poisonous; and they exist only in inconsiderable quantities. So far as is known, the ptomaïnes may be simply resultants of the transformation of other principles during extraction, for "they sometimes exhale a perfume like that of certain flowers, as the orange or wildrose, and of certain aromas"—odors which it is well known are not found among those of cadaverous pu-
