328 PHILOSOPHICAL TKANSACTI0N8. [aNNO 1766. 



The consideration of these is sufficient to inform us of the nature of the first 

 order of the class of amphibious animals: let us now see what is to be said of 

 the 2d in our division of them, which are such as chiefly inhabit the waters, but 

 occasionally go on shore. These are but of 2 kinds, the eels and water serpents, 

 or snakes of every kind. It is their form that qualifies them for loco-motion on 

 land, and they know their way back to the water at will ; for by their structure 

 they have a strong peristaltic motion, by which they can go forward at a pretty 

 good rate, whereas, all other kinds of fish, whether vertical or horizontal, are 

 incapable of a voluntary loco-motion on shore; and therefore, as soon as such 

 fish are brought out of the water, after having flounced a while, they lie motion- 

 less, and soon die. 



Let us now examine into the reason why these vermicular fish, the eel and 

 serpent kinds, can live a considerable time on land, and the vertical and hori- 

 zontal kinds die almost immediately when taken out of the water; and, in this 

 research, we shall come to know what analogy there is between land animals and 

 those of the waters. All land animals have lungs, and can live no longer than 

 while these are inflated by the ambient air, and alternately compressed for its ex- 

 pulsion ; that is, while respiration is duly carried on, by a regular inspiration and 

 expiration of air. In like manner, the fish in general have, instead of lungs, 

 gills, or branchiae; and, as in land animals, the lungs have a large portion of 

 the mass of blood circulating through them, which must be stopped if the air 

 nas not a free ingress and egress into and from them; so in fish, there is a great 

 share of blood vessels that pass through the branchiae, and a great portion of 

 their blood circulates through them, which must in like manner be totally stopped, 

 if the branchiae are not kept perpetually wet with water; so that, as the air is to 

 the lungs in land animals, a constant assistant to the circulation, so is the water 

 to the branchiae of those of the rivers and seas; for when these are out of the 

 water, the branchiae very soon grow crisp and dry, the blood vessels are shrunk, 

 and the blood is obstructed in its passage; so, when the former are immersed in 

 water, or otherwise prevented having respiration, the circulation ceases, and the 

 animal dies. Again, as land animals would be destroyed by too much macera- 

 ' tion in water, so fishes would, on the other hand, be ruined by too much exsic- 

 cation: the latter being, from their general structure and constitution, made fit 

 to bear, and live in the water; the former, by their constitution and forms, to 

 breathe, and dwell in the air. 



But it may be asked, why eels and water snakes are capable of living longer 

 in the air than the other kinds of fish? this is answered by considering the pro- 

 vidential care of the great Creator for these and every one of his creatures; for 

 since they were capable of loco- motion by their form, which they need not be 

 if they were never to go on sho re, it seemed necessary that they should be ren- 



