CHAPTER II 



THE BREATHING APPARATUS OF FISH, THEIR 

 TEETH, AND ORGANS OF SENSE 



The Gills The Teeth The Sense of Touch The Sense of Sight The Sense 

 of Hearing The Sense of Smell. 



AN attempt to deal with the internal anatomy of fishes 

 would be not only beyond the scope of the present work, 

 which aims no higher than to give a popularly intelligible 

 description of the fishes found in British lakes and rivers, but 

 would also exceed the powers of the author. Nevertheless, 

 any review of these creatures which is more than purely 

 superficial must take account of the manner in which their 

 existence has been affected by residence in the water, and the 

 degree in which their principal organs have been modified in 

 conformity with their environment. 



The breathing apparatus of fish is of peculiar interest, 



owing to the density of the medium from which it is its 



office to extract dissolved oxveen. The water 



The gills. , . , . . 11 



which enters the mouth passes through a cavity 

 containing the gills or branchiae, which consist of a series of 

 cartilaginous rods, borne upon the convex or posterior face 

 of the branchial arches (Fig. III., 58, 61), and flattened and 

 tapered towards the free end. These are the branchial lamella, 

 each of which is enclosed in a mucous membrane containing 

 also the capillary blood-vessels. It is these capillaries which 

 give the gills their brilliant red colour ; they are fed by an 

 artery which sends a branch into every pair of lamella^ which 



