Professor Parkes has described and named the offensive gases and putrid vapours given off by churchyards.[105] Professor Pettenkofer has also proved the presence of carbonic acid gas in the ground-air under houses, and the effects produced by this pulse-lowering gas. Dr. Reid examined at Manchester some graves which had been dug some hours previously, and found that it was necessary to have recourse to mechanical or chemical ventilation before the men could descend into them. The carbonic acid gas simply flowed into these deeply dug graves from the porous surrounding soil, like so much water. In the same way also this poisonous gas finds its way into the churches whose floors are below the level of the churchyards. Professor Selmi, of Mantua, has lately discovered in the strata of air which has remained during a time of calm for a certain period over a cemetery, organisms which considerably vitiate the air and which are dangerous to life. This was proved after several examinations. When the matter in question was injected under the skin of a pigeon, a typhus-like ailment was induced, and death ensued on the third day.[106] [105] See foot-note, p. 53. [106] Dr. De Pietra Santa. The dangers of inhaling the atmosphere of churches or chapels under which burial-vaults are made use of or interments made, have been repeatedly pointed out.[107] In other lands besides our own have these dangers been suspected and detected. The Tuscan Government requested Signor Piattoli to thoroughly investigate the subject, and his report has been confirmed by eminent men of various nations. As having taken place in our own land, Dr. Copeland mentions the case of a gentleman who was poisoned by a rush of foul air from the grated openings on the sides of the church steps, and who died from a malignant fever in a few days' time, communicating the same to his wife with a fatal result. The same fever has been known to seize pew-openers when cleansing and shaking the mattings of the floor. After a vault had been opened, the smell was at times overpowering. It was the opinion of Mr. Chadwick, after examining some hundreds of witnesses of all kinds, that entombment in vaults was a more dangerous practice than interment in the earth, because of the liability of the coffins to burst. [107] 'In vaults the air contains much carbonic acid, carbonate or sulphide of ammonium, nitrogen, hydrosulphuric acid, and organic matter. Fungi and germs of infusoria abound.'--Dr. Parkes, 'Practical Hygiene,' 4th ed.