RESPIRATION 



47 



The air inhaled is taken into two chambers situated one on 

 each side above the gills, forming outgrowths from the ordinary 

 branchial chambers. Each contains a more or less rosette-like 

 structure, made up of a number of concentrically arranged, 

 shell-like plates with wavy edges, all richly supplied with fine 

 blood-vessels. Each air reservoir is in communication, not only 

 with the branchial chamber, but also with the pharynx, the 

 entrance from the throat being controlled by a special valve. 



Fig. 20. — ACCESSORY BREATHING ORGANS. 



A. Dissection of head of Climbing Perch (Anabas scandens) ; b. The same of an 



Indian Cat-fish (Saccobranchus fossilis) ; c. The same of an African Cat-fish 



(Clarias lazera). All about natural size. 



Air enters by this aperture and passes out through the external 

 gill-opening (Fig. 20a). 



The related Snake-heads (Ophiocephalus) , long, cylindrical 

 fishes with slightly flattened and somewhat serpent-like heads 

 (Fig. 2 1 a), inhabit rivers and ponds as well as stagnant pools 

 in the marshes. The larger species grow to a length of three or 

 four feet. Their habit of "walking" over land by the aid of 

 rowing movements of the pectoral fins is well known, and 

 Snake-heads are frequently exhibited as curiosities by Indian 

 jugglers. They are extremely tenacious of life, and are carried 



