NATURALISTS CABINET. 



Supposed utility of the gills. 



tion, the fish in the exhausted water were not so 

 active as before, upon shaking the glass which 

 contained them. In three hours more, the in- 

 cluded fish lay all at the hottom of the glass with 

 their bellies upwards; nor could they be made 

 to shake their fins or tail by any motion given 

 to the glass. They had a motion with their 

 mouths, however, which shewed that they were 

 not perfectly dead. On uncovering the vessel 

 which contained them, they revived in two or 

 three hours, and were perfectly well next morn- 

 ing; at which time those in the exhausted water 

 were also recovered. The vessel containing 

 these last being put under the receiver of an air- 

 pump; and the air exhausted, they all instantly 

 died. They continued at top, while the air re- 

 mained exhausted, but sunk to the bottom on 

 the admission of the atmosphere. 



It is imagined that the gills offish are intended 

 for an operation somewhat similar to that of the 

 lungs in other animals; their motion is very an- 

 plogous to our breathing; yet the use of air to 

 these creatures is difficult to be assigned; and 

 the means of obtaining what they want is not 

 easily to be accounted for, or rendered intelligi- 

 ble. The general explanation of this phenome- 

 non is, that the fish first take a quantity of water 

 into their mouth, which is driven into the gills ; 

 these close and keep the water which is swal- 

 lowed from returning by the mouth, while the 

 bony covering of the gills prevents it from going 



