252 MR. F. E. BEDDARD ON THE [May 1, 



3. Notes on the Visceral Anatomy of Birds. — No. II. On the 

 Respiratory Organs in certain Diving Birds, By Frank 

 E. Beddard, M.A., F.R.S.E., Prosector to the Society. 



[Eeceived May 1,1888.] 



This note is based on the examination of some Puffins (Frateraila 

 arctica) and of examples of two species of Penp;uins {Eudyptula 

 minor and Spheniscus demersus), all of which have come into my 

 hands for dissection at the Society's Gardens. 



The most noticeable peculiarity about the respiratory apparatus 

 of Fratercula, indeed the only one that I observed, concerns the 

 structure of the oblique septum (*' diaphragm thoraco-abdominale" 

 Sappey) ; the general relations of this fibrous septum, which shuts off 

 the lungs and the ' intermediate ' air-sacs from the abdominal cavity, 

 have been already described in the ' Proceedings ' of this Society ^ 

 by Prof. Huxley ; as that description applies perfectly to the three 

 birds treated of in the present note, I merely refer to it. I may 

 mention, however, that the best figure known to me illustrating the 

 general disposition of the thoracic and abdominal viscera of a bird 

 is to be found in Wiedersheim's ' Lehrbuch der vergleichenden Ana- 

 tomic der Wirbelthiere' ^ The oblique septum o/Fratercula is remark- 

 able for the fact that it is covered for a considerable area with a laijer 

 of muscular fibres. This layer of muscular fibres arises (fig. 1, p. 253) 

 from the pubis — from the proximal and larger balf of this bone ; it is 

 abundantly furnished with blood-vessels and nerves. The direction 

 of the muscle is oblique; it covers the hinder region of the oblique 

 septum, ending abruptly some little way in front of the posterior 

 attachment of the latter ; the oblique septum, as in other birds, arises 

 partly from the pubis, but the posterior limit of its attachment to 

 this bone is considerably further forward than that of the sheet of 

 muscle. This sheet of muscle, besides ending abruptly upon the 

 oblique septum in front, is attached below to the upper surface of 

 the sternum, and to the abdominal parietes along the last sternal rib. 

 On the left side of the body the sheet of muscles is attached to 

 the sternum along a line much closer to the attachment of the 

 umbilical ligament than on the right side. The muscular fibres 

 which make up the sheet of muscle are arranged in a parallel series 

 of comparatively thick bundles with transparent (? fibrous) inter- 

 spaces. 



The presence of this muscular layer is not, however, peculiar to 

 the Puffin. 



Prof. Huxley, in the paper already quoted, states that in the Duck 

 the oblique septum " contains, on each side, a layer of unstriped 

 muscular fibres." Judging from Prof. Huxley's figure (o/j. cit. 

 p. 565, fig. 2,m), the layer of muscular fibres in the Duck is by no 

 means so extensive as in the Puffin. Prof. Huxley particularly 

 states that he has been unable to discover any such fibres in Apteryx. 



1 P. Z. S. 1882, p. 560. 2 2te Aufl., Jena, 1886, p. 654. 



