614 



G A N N E T. 



brave the severest weather in all seasons, without 

 attempting to near the shore. 



" This contrivance may also be of the most im- 

 portant service to an animal which is constantly 

 exposed, even in the most inclement seasons, and 

 cannot quit its station without starving. Nothing 

 could possibly conduce more to its security against 

 intense cold, or be better adapted to preserve the 

 necessary temperature of animal heat, than the inter- 

 mediate air dispersed between the skin and the body, 

 since that element is found to be a non-conductor of 

 caloric. Upon this principle, what animal can be 

 more securely protected against cold, or retain its 

 vital heat so effectually, as the gannet, or such birds 

 as are almost surrounded with a body of confined air, 

 divided by cells, and intersected by membranes 

 between the skin and body, and that skin so amply 

 covered with a light porous substance, filled also with 

 air, and impervious to water ? The gannet is capable 

 of containing about three full inspirations of the human 

 lungs, divided into nearly three equal portions, the 

 cellular parts under the skin on each side holding 

 nearly as much as the cavity of the body. Now, as 

 a full or extraordinary inspiration of the human lungs 

 has been considered to occupy a space of about sixty 

 cubic inches, so the gannet is capable of containing 

 not less than one hundred and eighty cubic inches 

 of air at one time, subject to the will of the bird, 

 under certain impressions." 



The following account of this very singular organi- 

 sation of the gannet, which, though possessed in com- 

 mon with the cormorants and some others, is yet so 

 much more remarkable in the gannet as to be deserv- 

 ing of particular attention, is from the observation of 

 Messrs. Owen and Yarrell, read to the Committee of 

 Science of the Zoological Society in 1831. " In the 

 examination," say these able comparative anatomists, 

 " our attention was chiefly directed to the air-cells, 

 which, in this bird as in the pelican, have a most ex- 

 tensive distribution. We commenced by gentle but 

 continued inflation 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 completely filled, especially that which is 

 situated in front of the os furdforme. Being thus 

 satisfied that they all had a free communication 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 oppo- 

 site side collapsed, indicating the existence of aper- 

 tures of communication, although the septum which 

 ran along the middle line of the body appeared at 

 first sight imperforate. There was a free communi- 

 cation between the lateral air-cella of the same side 

 of the body from the os furdforme to the side of the 

 pelvis i but the air-cells in front of the os furdforme 

 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, clearly dissected, having the air- 

 cells extended above and below them ; the axilliary 

 ressels and nerves also passing bare and unsupported 

 by any surrounding 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. As none of these proceed- 

 ings had any effect on the air-cells in front of the os 

 furdforme, which still continued distended, it was evi- 

 dent that inflation by the humerus could not have 

 filled it, except through the medium of the lungs 

 themselves. We next proceeded to detach the inte- 

 gument from this air-cell, to see its shape and extent ; 

 this required to be done with great care, as it ad- 

 hered 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 surface of the air-cells ante- 

 rior to the os furdforme. The use of these muscles 

 appeared to be to produce instantaneous expansion 

 of the air from these external cells, and by thus in- 

 creasing the specific gravity of the bird, to enable it 

 to descend with the rapidity necessary 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 

 glands at the termination of the trachea, which are 

 noticed by Montagu, and which exist in addition to 

 the ordinary pair lying above the bronchia;. The 

 stomach corresponded exactly with the figure given 

 by Sir Everard Home (Comp. Anat.. p. xlvi.), the 

 pyloric orifice being provided with the bilobed valve, 

 which is there represented, though not described in 

 the text ; it evidently opposes a too ready egress of 

 the contents of the stomach." 



We have given these observations in the words of 

 the observant authors, and we shall not point out 

 the small discrepances which might perhaps be found, 

 upon Examining what those first quoted have said, 

 with an eye of severe criticism. The fact is, that 

 there is no'part of the animal structure of the real 

 use of which we know less, than of that power which 

 some animals have of inflating their bodies in whole 

 or in particular parts. The air under the skin of 

 the thorax in the gannet must render the whole 

 body of the animal more buoyant, and as little can 

 there be any doubt that it. can take off the concussion 

 which the bird would otherwise experience when it 

 plunges down from a height upon its prey ; and that 

 it has some pretty severe labour to perform, is almost 

 a necessary inference, from the strength of the skin 

 and its internal membrane, and the number of points 

 at which it is tied to the muscles, the keel of the 

 sternum, and other parts. But it is rather too much 

 to assume that this apparatus has any thing to do with 

 the preservation of temperature in the bird. There 

 is no such provision in the whole animal kingdom. 

 If dry cold is to be guarded against, that is, cold in 

 which water does not reach the skin, then fur and 

 down are the provisions ; and if moist cold, the pro- 

 tection usually consists of a layer of fat under the 

 skin, the latter theory of its action is what is most 

 likely ; and when we consider what injury the human 

 body may receive by plunging into water from a height 

 of not more than twenty or thirty feet, we can at least 

 guess at what the gannet encounters, when it not 

 merely falls, but shoots down with an impetus from 

 more than ten times the height. The gannet always 



