«S" FISHES IN GENERAL. IJ 



Section III. 



•Of the Refpiration^ Food, ^c. of Fifljts. 



In all animals, refpiration, or the admiffion of air into the 

 body, feema neceffary to the fupport of life. From the 

 evperiments that have been made upon fiflies, almof!: in 

 the infancy of fcience, it appears, that the}' are inca- 

 pable of fubiifling without air for any coniiderable time. 

 The cetaceous and cartilaginous fifhes, are fupplied with 

 the neceflai-y quantity of t1)is fluid, by means of lungs 

 like the terreftrial animals ; and hence the Svjedijh na- 

 turalift has arranged them in the fame clafs of beings *. 

 In the fpinous fillies, refpiration is performed by hrcinchicc, 

 ©r gills, without the cavity of the body j but the precife 

 manner in which this operation is carried on, is one of 

 thofe fecrets of Nature, which neither the glaffes nor the 

 knife of the anatomift have ever yet been able to de- 

 velope. The manner, indeed, in which the air is tranf- 

 mitted from the lungs of quadrupeds into the blood, is 

 perhaps equally myfterious, as its paflage from the 

 branchiae of fifhes into the arteries leading to the heart. 

 This difficulty Artedi confeffes f j and Rondeletius^ Need- 

 ham, and other philofophers, have in vain endeavoured 

 to explain it. 



Vol. III. C The 



• vide Syflema Naturae, lafl edition. 



f Quomodo aer intjet brajichias plfcium, difBcile cfl. diiftu. 



