230 PROCEEDINGS OF THE SCIENTIFIC ASSOCIATION, 
mines the incompatibility of the matter with the life of the 
structure in which it occurs. * 
The liver of fishes, in performing its function of separat- 
ing impurities from the blood, and of secreting fluids, 
necessary to digestion, must do all the increased depura- 
tory work attendant on the absence of lungs. Exhalations 
from animals living in aeriform fluids are properly excre- 
tions. Erom animals living in aqueous fluids, excretory 
action must be much modified, and in fishes it exists only 
by that energy of “ reduction ” in which the albuminous 
matters of the chyle evolve gases by the “process of com- 
pletion.” f (Prout’s Bridgwater Treatise). In reptiles the 
liver is large, in consequence of the low degree of respira- 
tion of that class of vertebrate animals ; for the same rea- 
son it is large in fishes, and very large among the inverte- 
brata. In fishes the gall-bladder is observed for the first 
time in the animal series, as we ascend from the inverte- 
brate to the vertebrate classes, but it is not constant in its 
* I have no experience of the manifestation of kreatine or flesh- 
crystals in fishes either occasionally or permanently poisonous ; but 
the ordinary chemical property of living structures as laid down by 
Dr. Prout, in the Bridgwater Treatise, book iii., ch. i., on the 
“ Chemistry of Organisation,” is, that “ the essential elements are 
hindered from assuming a regular crystallised form. The incidental 
matters entering into the composition of a living body apparently 
furnish to the organic agent new powers — which powers the organic 
agent has been endowed with the ability to control and direct, in any 
manner that, from the exigencies of the living organised being, may 
become -requisite.” Hasp ail in his “ Chimie Organique,” section 
1378, says : “ Jamais je n’ai aper(;u de crystaux dans le sein d’une 
cellule vivante et d’accroissement.” 
f “II y a des poissons,” says M. Ervmann, illustrating excretory 
modification in nutrition, “ qui avaLent l’air atmospherique et en 
convertissent I’oxigene en acide carbonique, en la faisant passer au 
travers de leur intestins. Tel est le cobitis — il se fait a la peau, et 
sous les ecailles une transmutation semblable.” — (Cuvier, Hist. Natu- 
relle des Poissons, vol. i., liv. ii., ch. vii.) 
