COMPARATIVE ANATOMY. t37 



motion, and gives itself up to where the water impels it. 

 The rest of the fins, therefore, so far as respects motion, 

 seem to be merely subsidiary to this. In their mechanical 

 use, the anal fin may be reckoned the keel ; the ventral 

 fins, out-riggers ; the pectoral muscles, the oars : and if 

 there be any similitude between these parts of a boat and 

 a fish, observe, that it is not the resemblance of imitation, 

 but the likeness which arises from applying similar me* 

 chanical means to the same purpose. 



We have seen that the tail in the fish is the great in- 

 strument of motion. Now, in cetaceous or warm-blooded 

 fish, which are obliged to rise every two or three minutes 

 to the surface to take breath, the tail, unlike what it is in 

 other fish, is horizontal ; its stroke, consequently perpen- 

 dicular to the horizon, which is the right direction for 

 sending the fish to the top, or carrying it down to the bot- 

 tom. 



Regarding animals in their instruments of motion, we 

 have only followed the comparison through the first great 

 division of animals into beasts, birds, and fish. If it were 

 our intention to pursue the consideration further, I should 

 take in that generic distinction amongst birds, the loeh 

 foot of water fowl. It is an instance which may be point- 

 ed out to a child. The utility of the web to water fowl, 

 the inutility to land fowl, are so obvious, that it seems im- 

 possible to notice the difference without acknowledging 

 the design. I am at a loss to know how those who deny 

 the agency of an intelligent Creator, dispose of this exam- 

 ple. There is nothing in the action of swimming, as car- 

 ried on by a bird upon the surface of the water, that should 

 generate a membrane between the toes. As to that mem- 

 brane, it is an exercise of constant resistance. The only 

 supposition I can think of is, that all birds have been orig- 

 inally water fowl, and web footed ; that sparrows, hawks, 

 linnets, ^-c. which frequent the land, have, in process 

 of time, and in the course of many generations, had this 

 part worn away by treading upon hard ground. To such 

 evasive assumptions must atheism always have recourse ; 

 and, after all, it confesses that the structure of the feet 

 of birds, in their original form, was critically adapted 

 to their original destination. The web feet of amphibious 

 quadrupeds, seals, otters, &c. fall under the same observia- 

 tion. 



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