91 



through the trachea, a pipe having been introduced into the upper 

 larynx : in a short time the integuments of the whole of the lateral 

 and inferior parts of the body rose, and the air-cells seemed com- 

 pletely filled, especially that which is situated in front of the os 

 Jurciforme. Being thus satisfied that they all had a free commu- 

 nication with the chest, we next proceeded to see at what points 

 these communications took place, and in what degree the air-cells 

 communicated with each other. For that purpose the air-cells on 

 the left side of the body were laid open, and shortly after those of 

 the opposite side collapsed, indicating the existence of apertures of 

 communication, although the septum which ran along the middle 

 line of the body appeared at first sight imperforate. There was a 

 free communication between the lateral air-cells of the same side of 

 the body from the os Jurciforme to the side of the pelvis ; but the 

 air-cell in front of the os Jurciforme remained still tensely inflated. 

 The lateral air-cells had a free communication with the cavity of the 

 chest at the axilla, at which part the air had entered these cells 

 during the inflation. The pectoral muscles and those of the thigh 

 presented a singular appearance, being as it were, cleanly dissected, 

 having the air-cells extended above and below them ; the axillary 

 vessels and nerves also passing bare and unsupported by any sur- 

 rounding substance through these cavities. We traced the air-cells 

 down the side of the humerus, ulna, and metacarpal bone, into all of 

 which the air entered, and even into the bone corresponding to the 

 first phalanx, which agrees with what Mr. Hunter has described 

 in the Pelican, (Animal (Econ. p. 92.) 



" As none of these proceedings had any effect on the air-cell in 

 front of the os Jurciforme, which still continued distended, it was 

 evident that inflation by the humerus could not have filled it except 

 through the medium of the lungs themselves. We next proceeded 

 to detach the integument from this air-cell to see its shape and ex- 

 tent ; this required to be done with great care, as it adhered pretty 

 closely to the skin and roots of the feathers : it was of a globular 

 form, about four inches in diameter, and communicated with the 

 thorax at its anterior aperture below the trachea. 



" Numerous strips of muscular fibres passed from various parts 

 of the surface of the body, and were firmly attached to the skin ; a 

 beautiful fan-shaped muscle was also spread over the external sur- 

 face of the air-cell anterior to the os Jurciforme. The use of these 

 muscles appeared to be, to produce instantaneous expulsion of the 

 air from these external cells, and by thus increasing the specific 

 gravity of the bird to enable it to descend with the rapidity neces- 

 sary to the capture of a living prey while swimming near the surface 

 of the water. 



" With respect to the general anatomy of this bird, it may be 

 observed that we found the two small glands at the termination of 

 the trachea, which are noticed by Montagu, and which exist in ad- 

 dition to the ordinary pair lying above the bronchia. The stomach 

 corresponded exactly with the figure given by Sir Everard Home 

 (Comp. Anat, pi. xlvi.), the pyloric orifice being provided with the 



