306 Trench National Institute. 



ihe su!/)ect was confined: the nature and qihantity of ibe 

 gases had not been- esiabhshcd, which were absorbed by 

 these an- mals in the act oF respiration ; and the result of 

 these phacnonicna, the chief object of the cxperimcnls of 

 Humboldt and Proven^Ul, is to elucidate these (juestions. 

 VVjth this view they first consider fishes in their natural 

 ftate, and respiring river waters; "they next examine the 

 action of the bronehiae on the ambient v\ ater impregnated 

 with oxygen and azote, carbonic acid, or a mixture of 

 hydrogen and oxygen, and they afterwards treat of the 

 changes produced by fishes on different aeriform fluids iii 

 which they are plunged. 



Seven tench [ciprimis tinea) wrre placed under a bell- 

 glass filled with river water, and which contained 4000 cu- 

 bic centimetres : after eight hours and a half respiration, 

 the fishes were withdrawn, and the analysis of the air still 

 remaining in the water showed tliat in this space of time the 

 fishes had absorbed ]45'4 of oxygen, 57*6 of azote; and 

 that 132 of carbonic acid had been produced. Hence it re- 

 sults, as observed by our authors^ " that by the respiration 

 of the fishes submitted to this experiment, the volume of 

 the oxygen absorbed exceeded only by two-thirds the 

 volume of the azote which had disappeared, and that no 

 more than one eighth of the former had been converted 

 into carbonif acirl/' 



Fishes suffer greatly in water entirely freed of air; aiuj 

 after CO minutes they fall motionless to the bottom of the 

 vessels. In pure oxygen these animal^ seem to respire 

 with avidity, and open their bronchias more widely. In 

 azote and hydrogen, they keep their bronchice close, seem 

 to dread the contact oi' these gases, and die very soon after 

 having been plunged into the \\ ater which contains them. 

 Carbonic acid kills them in a few minutes: but fishes do 

 jiot absorb oxygen and azote by their bronehiae alone : the 

 whole snrfaee of their bodies has the faculty of acting on 

 these gases, and of assimilating them. Alter having with- 

 drawn the fishes from watef ^saturated with the deleterious 

 gases, and analysed it, some jx)rtion of carbonic acid was 

 Found in the litjuid ; but as there had been no oxygen ab- 

 sorbed, it is probable, as observed bv Messrs. IlLnnboldt 

 and IVovencal, that it was not the result of respiration, but 

 that it had been exhaled from the surface of tlic bodv. 

 Such are the principal points in this work, whieh besides 

 contains other uscinl observations and interesting views on 

 the physiology of fishes, but wliich the limits of this re- 

 port do not permit us to. enter upon. 



In 



