THE STAG BEETLE. 279 



Take one of these insects, kill it by the " death- 

 bottle/' or by dashing it into boiling water, lay open 

 the head and jaws, and a most beautiful structure will 

 present itself. The jaws are then seen to be quite 

 hollow, the hard, horny material being a mere shell 

 enclosing a row of the air vesicles which have already 

 been mentioned. A similar arrangement will be found 

 in the head, so that strength and bulk are beautifully 

 united with lightness. Any of my readers who are 

 students of comparative anatomy will remember that 

 in the elephant these three qualities are combined in a 

 very similar manner, the bulk of the skull being com- 

 posed of bony, comb-like cells. 



The thorax has many of these cells, and in the 

 abdomen they occupy a very large space, especially 

 towards the base of the abdomen, where it joins the 

 thorax. If a large beetle be rendered insensible by 

 chloroform, and the upper part of the head removed, 

 these vesicles can be plainly seen, swelling and lessen- 

 ing with every inspiration and expiration. 



We may be justified, therefore, in taking the in- 

 sects as best representing the denizens of air. 



Next to them come the Birds, in which there is a 

 lightness of structure analogous to that of the insects. 

 I have already mentioned that in the flying birds the 

 bones are hollow, and connected by certain apertures 

 with the air of the lungs. In Bennett's " Whaling 

 Voyage," a curious adventure is narrated, which very 

 well illustrates this peculiarity of structure. 



"Another bird which we noticed at the same 

 time is a nondescript, but nearest allied to the alba- 

 tross family. It is the size of the lesser albatross ; 



