Ixxviil 



which this species is found, that will explain the necessity of 

 it, or account for its presence, or is there any peculiar power 

 or faculty possessed by this bird of which those allied to it 

 are deprived ? or are we to regard it as one of those examples 

 of creative omnipotence which often displays itself in the va- 

 riety of its works, without any other obvious result but the 

 mere manifestation of that power? — a remark which appears 

 strongly verified by many of the peculiarities of the living 

 productions of Australia. 



Dr. Knox considers that the emu has been furnished with 

 this peculiar provision to preserve it amidst those dangers 

 from sudden floods to which New Holland is particularly 

 exposed. " The sandy plains of this country," he says, " are, 

 during a great part of the year, inundated, and become then 

 boundless marshes ; and the plains generally are exposed to sud- 

 den inundations. The rivers, moreover, running westward from 

 the great chain of mountains, terminate in vast muddy inland 

 marshes ; the emu, forced to seek his food amidst these fens, 

 may, when obliged to have recourse to swimming (which 

 must often be the case), fill the muscular bag of the trachea 

 with air, and thus convert it into a swimming bladder. It may 

 also assist the bird in escaping from his pursuers ; but on this 

 I do not mean to insist, as this organ is wanting in the galea- 

 ted cassowary and in the ostrich, both equally remarkable for 

 speed of foot." Dr. Knox further remarks, that when the 

 bag has been distended by an expiratory effort, and the glottis 

 retained in a closed state, the air may be alternately circu- 

 lated between the lungs, air-cells, and tracheal bag, without 

 the bird being necessitated to allow it to escape, in order 

 again to perform the act of inspiration, and thus give it an 

 additional advantage in running. This explanation appears 

 extremely probable, and, no doubt, if the inspiratory efforts 

 are thereby rendered less frequent, this creature may be ena- 

 bled to sustain its running flight (which, in speed, is said to 

 surpass the race-horse or the grey-hound) for a longer time, 



