CHEMISTRY OF THE LEDCOM AINES. 341 



metallic mercury. With silver oxide it forms pearly lanceo- 

 late plates having the composition C^HjNjO^.Ag. It does 

 not give any alkaloidal reactions. 



Undetermined Leucomaines. 



Leucomdines of Expired Air. 



It was shown at quite an early period that exhalations 

 from animals contain, besides an increased amount of car- 

 bonic acid, some organic matter, the nature of which, on 

 account of the exceedingly minute quantity in which it 

 occurs, has never been satisfactorily determined. Never- 

 theless, various observers did not hesitate to ascribe to it 

 the ill effects consequent upon breathing impure air, while 

 .at the same time the carbonic acid formed during respira- 

 tion was considered as either entirely inert or as insignifi- 

 cant in its action. Thus, respired air from which moisture 

 and carbonic acid have been removed, but which still contains 

 the organic vapors, has been found to be highly poisonous. 

 On the other hand, if the respired air is drawn through 

 a red-hot tube to destroy the organic mattex', the air thus 

 purified is capable of sustaining life even in presence of a 

 large percentage of carbonic acid. While it cannot be, 

 therefore, doubted that the organic matter of expired air 

 plays a most important part in producing the well-known 

 noxious effects resulting from breathing confined and vitiated 

 air, nevertheless it would seem from experiments made by 

 Angus Smith that the increase of even such small quanti- 

 ties of carbonic acid in the air, as from 0.04, the normal 

 amount present, to 0.1 per cent., is capable of producing 

 systemic disturbances characterized by a decrease in the 

 pulse-rate and an increase in the rate of respiration. 



Smith is consequently of the opinion that the constant 

 lowering of the pulse in impure air occasioned by the pres- 

 ence of carbonic acid must have a depressing effect on 

 the vitality. Whatever ill effects the carbonic acid may 

 produce of itself, it remains certain that this gas is not the 

 most potent and most injurious constituent of respired air ; 



