870 FISHES. 



M. Ehrmann, and even in all there is a similar transmutation on their 

 skin or under their scales. 



AVhen fishes remain out of the water they perish, not on account of 

 the want of oxygen, but because their gills become dry*, and the 

 blood cannot circulate there easily : also the species in which the 

 branchial orifice is narrow, as the eel, or those which possess some 

 receptacle in which they preserve Avater, as the anabas and the 

 ophicephilus, subsist for a longer time in the air, whilst those in 

 which the gills are very cleft, as the herring, expire the instant they 

 are taken from the water. 



Particular Excretions and Secretions. 



The excretions of fishes, as those of the other animals, are performed 

 either by the skin, or by special secretory organs. 



The kidneys are more voluminous in them than in any other class, 

 and extend on both sides of the spine along the abdominal cavity, 

 often ascending as far as under the base of the cranium and above 

 the gills and the heart : they are often united to each other by their 

 posterior part, and even, in> almost all the acanthoptcrygians, they 

 unite at their anterior part above the oesophagus. In the perch this 



Some fishes, when exposed to the air, soon cease to move their gills, although 

 they continue to live pretty long afterwards ; but they die much sooner than those 

 of the same species whose gills beat to the last. Suspecting that this difference in 

 the duration of life proceeded from the interception of the air, I remedied it by 

 raising the gills by a small peg placed beneath them. The branchise were thus ex- 

 posed to the air. This change of condition, in relation to the atmosphere, proved 

 sufficient to protract life as long as in those cases in which the respiratory move- 

 ments were continued spontaneously. The effect of thus raising the gills is so con- 

 siderable, that if the gills of a fish, out of water, have quickly ceased to beat, we 

 may, by its means, restore for a while, their spontaneous action, and even do so for 

 several times in succession. We see, therefore, that the life of fishes in the atmo- 

 sphere, depends on several conditions ; of which the principal are, temperature, the 

 capacity of saturation with water, the corresponding loss by perspiration from the 

 trunk and gills, the quickness of this loss, the action of the muscles which moves 

 the gills, and the use which they make of their muscles to avail themselves of the 

 action of the air upon the gills. In short, they come under the general law, rela- 

 tive to the influence of the atmosphere on the life of vertebrated animals. As fishes 

 seem to form an exception to this law, I have thought it necessary to shew that 

 they are so only in appearance. Wliat has been here stated relative to the life of 

 fishes in the atmosphere, is equally applicable to tadpoles, placed in the same cir- 

 cumstances. They die from the quantity of water which they lose by perspiration, 

 and although their capacity of saturation is, at least, equal to that of frogs, since 

 it varies between one -third and one-fourth of their weight, yet, as their size is very 

 small, and their perspiration rapid, on account of the delicacy of their skin, they 

 soon lose that proportion of water, and in the experiments which I made, I found 

 that they did not live more than four hours." 



We shall conclude our account of fishes by mentioning that in their case too, as 

 well as in all others connected with the animal and vegetable kingdoms, there is 

 evidence that they ai-e subject to the same general laws as nature has imposed on 

 every member of her vast dominions, namely, that there are many instances of 

 exception to this incapability of enduring high temperatures. It is proved that some 

 fishes actually live exclusively in hot springs which are literally three times higher in 

 temperature than the water by which Dr. Edwards killed fishes in a few minutes. — 

 Eng. Ed. 



* See Edwards, Influences des agens physiques sur la vie. 



