560 FROF. HUXLEY ON THE RESPIRATORY [JunC 20, 



2. On the Eespiratory Organs of Apteryx. By Thomas 

 H. Huxley, F.R.S., F.Z.S. 



[Eeceived June 2, 1882.] 



1 am not aware that the structure of the respiratory organs of 

 Apteryx has been investigated since the pubhcation of Professor 

 Owen's Memoirs on the Anatomy of the Southern Apteryx, in the 

 second and third volumes of the ' Transactions ' of this Society. 

 Professor Owen gives a detailed description of a structure which he 

 terms the diaphragm, and compares it with that organ in mammals ; 

 the account of the anatomy of the lungs and of the air-sacs, on the 

 other hand, is less full. The important fact that no air-sac extends 

 into the abdomen is noted ; but only four air-sacs on each side are 

 mentioned, and no attempt is made to identify these with the air-sacs 

 of other birds. 



The question whether Apteryx presents any real approximation to 

 mammals in the structure of its breathing-apparatus is of consider- 

 able interest, from its bearing upon the general problem of the 

 affinities of birds to other groups of vertebrated animals. Having 

 recently examined a specimen of Apteryx (which, although it had 

 been many years in spirit, was still in a very fair state of preserva- 

 tion) with reference to this point, I have come to the conclusion that 

 its respiratory organs differ in no essential respect from those of 

 other birds — though they exhibit those peculiarities which are 

 peculiar to and characteristic of the class Aves in a less developed 

 condition thau that which obtains in all those Carinatse and Ratitse 

 which have been carefully studied. 



The admirable monograph by Sappey ', chiefly based on the study 

 of the respiratory organs of the Duck, contains the most complete and 

 accurate account extant of the general disposition of these organs in 

 their highest condition of development. Rainey ^ supplemented this 

 by the important discovery of the existence of intercapillary air-pas- 

 sages; and, more recently, Campana^ has contributed a very elaborate 

 study of the respiratory organs of the Common Fowl. It is not diffi- 

 cult to verify the chief statements of these anatomists. Nevertheless 

 it is any thing but easy to find a succinct and precise account of the 

 facts ; and the terminology at present employed appears to me to be 

 for the most part cumbrous and inappropriate. I make no apology, 

 therefore, for endeavouring to amend this state of matters. 



The lungs of birds lie, one on each side of the vertebral column, 

 between the first thoracic rib in front and the anterior end of the 

 kidney behind. On the dorsal aspect they rise, on the sides of the 

 vertebrae, as high as the tubercular transverse processes of the ribs. 

 On the ventral aspect they descend to a variable distance towards the 



^ Recherches sur I'appareil respiratoire des Oiseaux : 1847. 



2 " On the minute Structure of the Lung of the Bird," Medico-CIiirurgical 

 Transactions, xxxii. 1849. 



2 Les lois de rEvolution animale. — La respiration des Oiseaus : 1875. 



