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Show 1867.J DR. E. CRISP ON THE HIPPOPOTAMUS. 609 posterior edges flattened and measuring $ inch in width. The au-terior edges, which form the glottis, are thin ; and by their apposition the glottideal slit is entirely closed. The vocal ligaments are very slightly developed. The state of the larynx and of the surrounding parts prevented my making a careful inspection of the laryngeal muscles, an investigation that will fully repay future inquirers. The trachea consists of twenty-three rings ; it is of moderate calibre (1 inch), less capacious than in many young non-aquatic animals ; its size is nearly uniform ; and, as in most quadrupeds, it has three terminal branches, the two on the right side being nearer together than usual. 1 have placed the larynx and trachea of the Porpoise and Dolphin on the table to show the resemblance of the upper part of these tubes to that of the Hippopotamus. The heart is of a rounded form ; it weighs 21 ox. ; its length from the root of the aorta to the apex 6 inches, and its width at the base the same. The external course of the coronary arteries is well marked, their mouths large and in the usual situation. The pulmonary artery of very large calibre. The aorta also of large size, its coats one-third thicker than those of the last-named vessel. The first large primitive branch (innominata) is l£ inch from the semilunar valves, the second (subclavian), about one-half its calibre, close to it. The coats of the first-named arterial branch are of unusual thickness. The aortic and pulmonary semilunar valves present nothing worthy of notice, except that they have no corpora Arantii. The ventricles are nearly of equal size, the left being rather more capacious. The sides of the right ventricle are generally smooth, whilst those of the left are reticulated ; numerous cross bands are present at the apex of this ventricle, all passing in the lateral direction of the cavity. The parietes of the left ventricle measure about 1 inch in thickness, whilst those of the right are ouly Jj- inch. The septum is very thick, measuring at its upper part I| inch in thickness. The tendons of the mitral valve, fifteen in number, arise from two fleshy columns, the posterior being much larger than the anterior, although less prominent. The tendons of the tricuspid valve, seventeen in number, spring from three columns (so called), one prominent aud nipple-like, the others but little raised above the surface. The cavities of the auricles are of about the same capacity ; but the appendix of the right auricle is larger, and its parietes thinner and more distensible. In both appendices the musculi pectinati are very numerous, those in the right forming a double reticulated layer of bands, and presenting a very beautiful appearance. The foramen ovale is deep and about the size of a shilling; it is perfectly closed, and a small nipple-like process projects from its centre. The projection at the upper part of the circle (isthmus Vieusseni) is well marked. The Eustachian valve is but imperfectly developed ; indeed, with the exception of a slight semicircular elevation, it can scarcely be said to exist; there is no tubercle of Lower so-called. The openings of the two coronary veins are seen an inch below the foramen |
