NATURALIST'S CABINET. 



Observations by Dr. Munro. 



phagus, stomach, or intestines. The air-bag was 

 not enlarged by blowing into the alimentary ca- 

 nal, nor could it be emptied without bursting it. 

 Further, on the inner side of the air-bag of the 

 cod, haddock, &c. was found a red-coloured 

 organ, the surface of which is very extensive, 

 composed of a vast number of leaves or mem- 

 branes doubled; but in thdse fish where the air- 

 bag communicates with the alimentary canaf, 

 this red body is either very small and simple in 

 its structure, as in the conger-eel, or entirely 

 wanting, as in the sturgeon, salmon, carp, Sec. 

 Hence, he thinks it reasonable to suppose, that 

 the air may be secreted from this red body, 

 somewhat in the same way it seems to be secreted 

 into the swimming-bladders of aquatic plants, or 

 perhaps into the air-bag of the egg of a bird as 

 the chick grows. Many naturalists, however, 

 may be of opinion, that the cod, haddock, &c. 

 has an air-duct, which has yet escaped ob- 

 servation. 



.Dr. Munro, in all the fish which fell under his 

 dissection, found the heart to consist of but one 

 ventricle ; and that from the latter one artery is 

 sent out, which is entirely spent on the gills. 

 That from the gills, therefore, the returning 

 blood passes to all the other parts of the body, 

 without the intervention of a second auricle, as 

 in man. From his observations and experi- 

 ments, the doctor concludes, that the circulation 

 of the blood being carried on in the cartilaginous 



