KESPIltATION OF FISHES. 
117 
The gymnoti, like our eels, are fond of swallowing and 
reathing air on the surface of the water; but we must not 
hence conclude that the fish would perish if it could not 
°ome up to breathe the air. The European eel will creep 
curing the night upon the grass; but 1 have seen a very 
'Jgorous gymnotus that had sprung out of the water, die on 
Ie ground. M. Provencal and myself have proved by our 
1 ‘ searches on the respiration of fishes, that their humid 
•’oiiehuc perform the double function of decomposing the 
o mosphcric air, and of appropriating the oxygen contained 
n Wa ter. They do not suspend their respiration in the 
®F{ [ )ut they absorb the oxygen like a reptile furnished 
^ ith lungs. It is known that carp may be fattened by being 
’ ou .t of the water, if their gills are wet from time to 
jime with humid moss, to prevent them from becoming dry. 
't 1 separate their gill-covers wider in oxygen gas than in 
• ater - Their temperature however, does not rise ; and they 
~ - e the same length of time in pure vital air, and in a 
feature of ninety parts nitrogen and ten oxygen. We 
a , Unc ! that tench placed under inverted jars filled with air, 
a 5° r h half a cubic centimetre of oxygen in an hour. This 
Co |, lon takes place in the gills only; for fishes on which a 
of th COr k ^ as t>oen fastened, and leaving their head out 
the jar filled with air, do not act upon the oxygen by the 
res tof their body. 
in .) 10 s ' v hnming-bladder of the gymnotus is two feet five 
f.'j'j 8 , lon g in a fish of three feet ten inches.t It is sepa- 
‘ ; he < U ] a . mass °t fat from the external skin ; and rests upon 
electric organs, which occupy more than two-thirds of 
PowerfM ^ different. The Indians mentioned to us a black and very 
att a ; n U * ?P ec * es < inhabiting the marshes of the Apure, which never 
Piocur 3 more than two feet, but which we were not able to 
Uiid er Vi rafon of the Rio de la Magdalena, which 1 have described 
v°i. j Vl.' e name of Gymnotus sequilabiatus (Observations de Zoologie, 
without ° rms a Particular sub-genus. This is a Carapa, not scaly, and 
Brazil^ a V. t ‘ ectr ’ c or g an - This organ is also entirely wanting in tha 
Ouvie r an ^ ara l' 0 ’ an( i in all the rays which were carefully examined by 
°esid es U j! er ^ ias 8 ^® wn that in the Gymnotus electricus there exists, 
8tln aller i ar £ e swimming-bladder, another situated before it, and much 
^ ^ 0 °ks like the bifurcated swimming-bladder in the Gymnotui 
