LARUS ARGENTATUS, HERRING GULL. 631 



equal portions by a crescentic fold or reduplication of mncous membrane. The anterior 

 or internal of this is the cloaca proper, and is greatly the largest ; the posterior or ex- 

 ternal forms the "bursa Fabricii," and consists merely of a bnlging or unequal dilatiou 

 of that portion of the cloacal parietes that is beyond the curved fold of mucous mem- 

 brane already mentioned. Just beside this fold, about a fourth of an inch on either 

 side of the median line, on the posterior aspect of the cloaca, are two small papillae, 

 placed side by side and in close contact. On the summits of these papilhe terminate 

 the ureters and vasa deferentia, the excretory ducts of the sexual and urinary organs. 



The pancreas occupies the whole length of the concavity of the duodenal fold. It is 

 therefore of an elongated shape, and is somewhat triangular on a cross-section. The 

 rounded free extremity of the gland is rather larger than the other end, the whole 

 organ being somewhat club-shaped. Its long slender duct opens into the duodenum 

 between the hepatic and cystic ducts. The two lobes of the liver are of very unequal 

 sizv^, the right being much the largest. It measures about three inches in length, while 

 the left is only a little over two. Their internal or apposing surfaces are flat, and in 

 contact for the greater part of their length, only separating above to admit the apex of 

 th" heart between them. They are both somewhat of a triangular shape on a cross- 

 section ; rising up high, and thick in the middle ; tapering toward both extremities; 

 the right being the most elongated and attenuated. They are somewhat loosely con- 

 nected by a thin, flat band of hepatic substance. The surface of both presents several 

 eminences and depressions, produced by the impact of neighboring organs and parts. 



The hepatic duct proceeds from the middle of the under surface of the left lobe, near 

 the commissure ; has a length of about two inches, and opens into the duodenum, as 

 already described. • 



The gall-bladder lies in a depression on the under surface of the right lobe, and is 

 well developed. It is of an ovoid shape, tapering toward its proximal extremity ; 

 more obtuse at its distal. The cyst-hepatic duct is very short, opening directly into the 

 base of the bladder. The cysti.c duct arises about midway between the two extremi- 

 ties of the bladder, on its posterior aspect. It is larger, but shorter than the hepatic 

 duct, and opens into the duodenum an inch further down. 



The kidneys measure about two and a fourth inches in total length, but are of very 

 varying breadth at different points along their extent. They are irregularly divided 

 into several lobes, which are not, howevei", of regular shape, and closely adapted to 

 each other, aa in Sterna ; nor do they ax)pear to be constant as to their mode of subdi- 

 vision. The upper lobe of each is the largest, and has the most convex outline. The 

 next is very narrow, serving as a connection between the anterior and posterior ex- 

 tremities, and is sometimes almost divided into two. The i)osterior lobe is nearly rect- 

 angular in shape ; about twice as long as broad ; and has a deep, longitudinal sulcus 

 upon its surface, in which is received the ureter. 



Tlie sexual organs lie superimposed upon the superior lobes of the kidneys, closely 

 bound down to them. Their eft'erent ducts run along in close apposition with the 

 ureters, and terminate in the cloaca side by side with the oritices of the tirinarj- ducts, 

 as has been already describetl. 



The superior larynx is composed of four principal elements : A thyroid cartilage, two 

 arytenoid, and a cricoid, the latter divided into three separate portions. The thyroid 

 is much the largest of these, forming all of the anterior or inferior i)ortion of the organ. 

 It is of a tapering, subconical form, with an ovoid truncated extretnity, and an obtuse 

 tip. Its lateral edges curl over upward, especially posteriorly, where it supports the 

 cricoid, forming all of the cartilaginous lateral parietes which the larynx posses.ses. 

 Its inft'rior surface is nuirked with a longitudinal groove; its internal with a well-de- 

 veloped eminence, situate ou the median line, not distantly reseml)ling the crista galli 

 of the human ethmoid bone. Anteriorly the thyroid extends forward as a ujere flat 

 lamina, with scarcely any convexity. The posterior portions of the thyroi 1 support 

 the two lateral elements of the cricoid. These are quite broad at their base; curl over 

 toward the median line ; growing narrower as they approach each other, till they com- 

 plete the circle of the larynx posteriorly by uniting with the central azygoid clement. 

 This is a small, irregular, cartilaginous noduli-, situate on the median line, having, pos- 

 teriorly, two surfaces for the rcctiption of the lateral cricoid elements ; more anteriorly 

 two others for the articulation of the two arytenoid cartilages. These latter are of 

 denser consistency than the rest of the larynx, being sometimes almost oSseotis. 'I'iiey 

 are four-tenth.s of an inch long. Their l)ase presents ou their inner surfaces the facet 

 for the articulation with the azygos element of the cricoid. They are so twisted or 

 curled u](on their own axes, that their lateral edges, at lirst horizontal, are atlerward 

 perpendicular, rising above the level of the rest of the larynx, and lying parallel to 

 each other, thus forming tin; rima gloltidis. These several cartllagRions pieces ot' the 

 larynx are all connected by a delicate, clastic, libro-cellular tissue. The motion which 

 they possess is limited almost «'ntirely to thiMipening and shntfiug of the arytenoid 

 cartilages, eflected by the nuiscles attached to them ; tin; motion being chiefly at the 

 aryteno-cricoid articulation. These proper muscles of the larynx are the tliyro-ary- 



