346 CLASS XVI. 



many species of clucks, and in the genus Mergus, in the males, 

 there are lateral expansions at the origin of the bronchi, which are 

 developed unsymmetricallj, so that the swelling on the left side is 

 usually the larger. In the ducks they are usually bony vesicles, in 

 Mergus large many-sided spaces, with bony margins, between which 

 a stout membrane is stretched ^ The superior larynx is situated 

 under the base of the tongue. It consists of ossified cartilages, of 

 which the largest is high in front and triangular, low behind, annu- 

 lar and not completely closed, and corresponds to the thyroid carti- 

 lage of man. The posterior part of the ring is formed by a small 

 cartilage, the cricoid, which projects beyond the ring upwards. On 

 each side of this projecting portion lies a triangular elongated part; 

 between these two [arytceno'id cartilages), which are concave on 

 their inner surface, lies the glottis; it presents no vocal ligaments, 

 and can be narrowed and widened, but not stretched and slackened. 

 The anterior and upper part of the thyroid cartilage has sometimes 

 an epiglottic process, which mostly remains cartilaginous; more 

 rarely is there found here a moveable appendage as a vestige of an 

 einglottis, which, as a rule, is totally wanting in birds. Conical, 

 horny papilla, with their points turned backwards, generally sur- 

 round the base of the tongue and the glottis; they prevent particles 

 of food from falling into this fissure. Also a transverse fold of the 

 mucous membrane is mostly found in front of the glottis, under 

 which the larynx, which in deglutition is drawn forward, can 

 retreat '\ 



The kidneys are large, and are situated in a depression of the 

 iliac bones; they have a dark-red colour and a soft tissue, in which 

 no distinct cortical and medullary substance is observed. The ex- 

 ternal surface presents convolutions which resemble those of the 

 brain of mammals. Here are found the terminations of the tor- 

 tuous secretory uriniferous tubules, which are pennated on each 

 side by blind terminal branches that run parallel to each other. 

 In the interior of the kidney the tubules unite to form larger tubes 

 which are collected into bundles, from which the branches take 



^ Yareell, 1. 1. Tab. 15; compare also Rosenthal Abhandlungen aus dem Gebietc 

 der Anat. Physiol, u. Pathologic, Berlin, 1824, 8vo, s. 40 — 75, Tab. iv. 



2 Meckel Syst. d. vergl. Anat. vi. s. 464 — 469, and especially Henle Vergleichend 

 A'natomische Beschreibung des Kehlkopfs, Leipzig, 1839, 4to, pp. 54 — 66. 



