THE COMPOSITION OF EXPIRED AIR. 399 



was usually closed ; tins was only used for the removal of air for its 

 chemical examination. In the beginning thermometers and hygrome- 

 ters were used in the vessels, but they were found to be unimportant 

 and were abandoned. The whole apparatus was connected with a large 

 aspirator. 



In an experiment with five animals and a ventilation of 4 liters per 

 hour, the carbonic acid was found to amount to 9.3 per cent after five 

 hours. In another experiment with six animals ami with a ventilation 

 of 2£ liters per hour, he inserted four absorption tubes, with soda lime 

 between the last two jars, and a Geissler tube containing concentrated 

 H 2 S0 4 between the fourth and fifth. The sixth animal remained alive, 

 while the fifth died earlier than the fifth animal in the first experi- 

 ment. He concludes that there is no organic poison in expired air, 

 death being due to the excess of carbonic acid in the atmospheres of 

 the jars. 



Sanfelice, in 1893 (27), reported that he had repeated the Ham- 

 mond experiment, using a flask of about 5 liters' capacity, the animal 

 dying in six or seven hours. He is undecided as to the existence of a 

 volatile expiratory poison, though he thinks that other factors, for 

 instance, heat radiation, have an important influence upon the results. 



Liibbert and Peters, in 1894 (28), reported that they had repeated 

 the Brown-Sequard experiment, placing a guinea pig in each of a 

 series of four flasks. Between the third and fourth flasks they placed 

 a combustion tube through which the air coming from the third flask 

 was conducted, passing over red-hot cupric oxide, to remove the organic 

 matter. Before reaching the fourth flask, the air was again cooled by 

 conducting it through a cylinder surrounded with ice. In this manner 

 all moisture contained in the air was condensed. From this cylinder the 

 air passes through a series of twelve U-tubes, each made from a piece of 

 tubing 80 centimeters in length and of 2 millimeters internal diameter. 

 During its passage through these U-tubes the air assumed a tempera- 

 ture of about 18° C. as it entered the fourth flask. The results obtained 

 by this arrangement substantiated the conclusions they had formed from 

 conducting the experiment in the ordinary manner, that the cause of 

 death was traceable to the high per cent of carbonic acid. The removal 

 of the organic matter by combustion failed to save the life of the animal 

 in the last jar when the carbonic acid had increased to 11 or 12 per cent. 

 After the absorption of the carbonic acid by means of soda lime the 

 last animal remained alive. They conclude, therefore, that the poison- 

 ous expiratory poison of Brown-Sequard and d'Arsonval does not exist, 

 but that death is produced by the excess of carbonic acid in the flasks. 



Brown-Sequard and d'Arsonval, in 1894 (29), reported further exper- 

 iments, and at the same time gave fuller details as to all their experi- 

 ments and the apparatus employed. They had inoculated over 100 

 animals with the condensed fluid of respiration and believed in the 

 truth of their former statements as firmly as ever. They could not 



