Ixix 



Meckel, in the tenth volume of his Comparative Anatomy, 

 alluded to the discovery of this air sac by Fremery, in the 

 year 1819, but states that he has noticed it in a vague and 

 imperfect manner. I have not had an opportunity of consult- 

 ing this work of Fremery. Meckel does not describe this air 

 sac with that clearness and precision so characteristic of this 

 writer. His account rather consists of quotations from Knox, 

 and of the varying statements of other writers, than of any 

 observations of his own. Carus, in his System of Compara- 

 tive Anatomy, makes no mention of it. It does not appear 

 to have been known to Cuvier, as there is no notice of it 

 either in his Anatomie Comparee, or in his Regne Animale, 

 neither is it alluded to in the new edition of that invaluable 

 work, now in course of publication. In the elaborate and 

 excellent article " Aves," in the Encyclopaedia of Anatomy 

 and Physiology, edited by Dr. Todd, of London, and which 

 article is from the pen of Mr. Owen, who is justly regarded 

 as the first comparative anatomist and zoologist of the present 

 day, this peculiar appendage is alluded to ; but, strange to 

 say, the brief and imperfect account which is there given of it 

 is wholly incorrect, a circumstance I can only attribute to 

 some accidental inadvertence. Mr. Owen says, " that the 

 trachea of the emu is remarkable for a sudden dilatation; 

 but, in this instance, the cartilaginous rings do not preserve 

 their integrity at the dilated part, but are wanting posteriorly, 

 where the tube is completed by membranes only." I have 

 made some researches into the writings of other authors also, 

 but have not met with any accurate description of this appa- 

 ratus. 



As I have lately had an opportunity of examining this 

 appendix in the living bird, as well as in one recently dead, 

 I shall state such facts as I have observed in the former con- 

 dition, as well as the appearances 1 have remarked in the 

 latter. I may first observe, that this exists both in the male 

 and female ; for some time since I dissected a male emu, and 



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