206 THE VOYAGE OF H.M.S. CHALLENGER. 



SO far back as to come into relation with, and have any effect upon the organ of voice. 

 This probably explains the persistently braying character of the voice of the Penguins, 

 which all who have listened to these birds in their native haunts describe as being 

 uniform in tone, and capable of but little modulation. 



The Bronchial Tubes. — Each of the bronchial tubes, from the point of bifurcation 

 of the trachea to the corresponding lung, measures in Eudyptes chrysocome from Tristan 

 d'Acunha 1 inch in length. Each diminishes in diameter from its commencement to its 

 termination. The bronchial rings, exclusive of those which enter into the formation of 

 the syrinx, are twelve in number, and, unlike those which form the trachea, are incom- 

 plete, and form a series of cartilaginous bars which are confined to the inferior or ventral 

 surface of the bronchial tube. The bronchial bars are soft and flexible, and therefore differ 

 from those met with in the trachea, which are rigid and osseous in character. The 

 bronchial bars diminish rapidly in length from before backwards. The dorsal wall of 

 each bronchus is entirely membranous from end to end, this membrane constituting the 

 vibrating plate already described in connection with the lower larynx. 



In both specimens of Eudyptes chrysocome from Tristan d'Acunha, which I ex- 

 amined, a peculiar dense fibrous pad (PI. XIX. fig. 1) was closely adherent to this mem- 

 brane. The exact nature or function of this body is difficult to determine, but that 

 it forms no essential part of the laryngeal or bronchial apparatus is shown by the fact 

 that it is absent in every other species of Penguin which I have dissected. This remark 

 holds good, not only of other species, but also of specimens of Eudyjitcs chrysocome from 

 the Falkland Isles (PI. XIX. fig. 3) and from Kerguelen, and were it not for the fact 

 that it was observed in two specimens of Eudyptes chrysocome from Tristan, I should 

 certainly have regarded it as an individual and possibly pathological occurrence. In 

 view of the fact stated, however, its occurrence ought probably to be regarded as a dis- 

 tinctive peculiarity of a local form of one species of Eudyptes. Farther research, how- 

 ever, is necessary to decide this point. The terminal portion of each bronchus is entirely 

 membranous and altogether devoid of cartilasfinous bars. 



Muscles of the Trachea and Bronchi. 

 1. Cleido-thyroid muscle. 



Steriio-thyroidien, Vicq d'Azyr, 1773, p. 581, No. 1. 

 Gahelknoehen-Liiffnihren-Muskel, Tiedemann, Bd. i. p. 667, No. 2. 

 Ypsilo-tracheens, Cuvier, vol. iv. p. 466. 

 Tpsilo-trachealis, Meckel, vol. x. p. 340. 

 Cleido-tracheen, Gervais and Alix, p. 17. 



Attachments. — The cleido-thyroid muscle (PI. VIII.) arises from the anterior border of 

 the clavicle, about ^ an inch from its junction with the bone of the opposite side. The two 



