French National Instltuie. 895 



of tb€ former hav€ been made on fishes in the Gulf of 

 Nice, and those of the latter were maxle on the fish<.*s in 

 the sea around the Balearic Islands. But the labours of 

 these naturalists have not been -confined to bringing new 

 species to light :— from their accounts there are grounds for 

 supposing that each species of fish, like terrestrial animals, 

 has a region, in tbe midst of which its existence is circum- 

 scribed, and that those of the south are never met with in 

 the north, and vice versa. M. Risseau, however, has dis- 

 covered in the Mediterranean some fijhes which had not hir 

 iherto been found except in the Indian or in the Northern 

 'seas. 



M. Delaroche has made some interes'ting researches as to 

 the depth at which each species of fish lives habitually, as 

 to the modes of fishing, and on the subject of the swim- 

 ining-bladder. 



PHYSIOLOGY. 



Physiological experiments of all others are those which 

 require most leisure and patience, while the rigorous exacti- 

 tude so important and necessary in the sciences is more 

 xiifficult of attainment in physiology than in any other 

 branch of experimental philosophy. Humboldt, however, 

 while occupied on a voyage in which obstacles and danger^ 

 were daily increasing, directed his attention to some deli- 

 cate experiments on several of the phasnomena of life. 

 He has communicated the researches which he made in 

 America on tb» respiration of the crocodile with the sharp 

 beak : he was led to ascertain *' that this animal, nolwith- 

 , standing the volume of its bronchiae and the structure of 

 its pulmonary celluli, suffers in an air which is not re- 

 newed ; that its respiration is very slow : — in the space of 

 lan hourand 43 minutes, a young crocodile, three decimetres 

 in length, took up only about 20 cubic centiemcs of oxy- 

 gen from the surrounding atmosphere." 



Since his return to France, M. Humboldt, in conjunction 

 with M. Provencal, has made some additional inquiries 

 into ihe respiration of fishes. The experiments of these 

 gentlemen, which are numerous, and remarkable for their 

 accuracy, have led them to very important results. 



The experiments of Spallanzani, and of our colleasjuc, 

 liad demonstrated that it is not by decomposing water that 

 fishes breathe, as some naturalists thought ; but by taking 

 up the oxygen dissolved in this liquid, or by corning to the 

 surface ot the water they collect it immediately from the 

 atii^osphere. To these observations all our knowledge pi\ 



<he 



