594 PHYSIOLOGY OF RESPIRATION. 



It seems to be clear that, when the expired air is condensed by pass- 

 ing it into a cooled chamber, the water thus obtained, about 100 

 c.c. for 2500 liters of air, is clear, odorless, and has only a minute 

 trace of organic matter. If this liquid with or without conden- 

 sation is injected under the skin or into the blood-vessels no 

 evil result follows, according to the testimony of the majority of 

 observers. But it remains possible, of course, that the substance 

 if present may be destroyed by this method or may escape precipi- 

 tation in the condensed water. The experiment that gives the 

 most positive indication of the existence of an organic (basic) poison 

 in the expired air is the following, first performed by Brown- 

 Sequard: A series of say, five bottles, each of a capacity of a 

 liter or more, are connected together in train so that air can be 

 drawn through them by an aspirator. A live mouse is placed in 

 each bottle, and between bottles 4 and 5 an absorption tube is ar- 

 ranged containing sulphuric acid. Under these conditions only the 

 mouse in bottle 1 gets fresh air, those in the successive bottles get 

 more and more impure air, while in bottle 5 this air is purified to the 

 extent of removing the organic matter by passing it through sul- 

 phuric acid. The result of such an experiment as described by 

 some observers is that the mouse in bottle 4 dies after a certain num- 

 ber of hours, the one in bottle 3 later, while those in the first and 

 last bottles show no injurious effects. The obvious conclusion is that 

 death in such cases is due to some organic toxic substance, and not 

 to a mere increase of carbon dioxid, chemical analysis showing that 

 this latter substance does not accumulate sufficiently under these 

 conditions to cause a fatal result. Some other observers have failed 

 to get this effect, but even assuming it to be correct it will be noted 

 that the experiment gives no proof that the organic substance in 

 question is excreted in the expired air. Indeed, the seemingly 

 very careful experiments of Formanek make it probable that in 

 these experiments the toxic substance is ammonia or an ammonia 

 compound, which is not given off from the lungs, but from the decom- 

 position of the urine and feces in the cage. When this latter source 

 of contamination is removed the expired air is practically free 

 from ammonia and without injurious effect. The expired air 

 therefore, according to work of this character, contains no organic 

 poison which can be regarded as a product of respiration. 



Some observers (Hermann, Haldane, and Smith) have made 

 careful experiments upon men which also seem to throw much 

 doubt upon the existence of such a substance. Individuals kept 

 in a confined space for a number of hours give no symptoms of evil 

 effects except when the accumulation of the carbon dioxid has 

 reached a concentration of over 4 per cent. At this concentration 

 rapid breathing is apparent, and if it rises to 10 per cent, great 



