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Show 1879.] ANATOMY OF HY.ENA CROCUTA. 87 placed higher in the laryngeal box than the posterior. They are (as is the case also in Proteles) separated from the base of the epiglottis in front and from the arytaeno-epiglottidean folds of mucous membrane of each side by a deep sinus, the mucous membrane of which is smooth and glistening. The space enclosed by the false cords is oval in form and of such width that the true vocal cords can be readily seen from above. The latter are much stronger and thicker than the false cords, and approach more closely to the middle line of the larynx ; between them is the rima glottidis, which is triangular in form. Judging from Mayer's figure of the larynx of II. striata, that of II. crocuta closely resembles it, differing, however, in the possession of well-marked false vocal cords, which, according to the author named, are absent in the former species. At the same time it is to be observed that Meckel1 does not deny the presence of both false and true vocal cords in the larynx of H. striata. Taken as a whole, the larynx of H. crocuta, like that of Proteles, as pointed out by Prof. Flower, presents a greater resemblance to that organ in the Felidae than in the Canidae, differing from the former, however, in the oblique position and diminished prominence of the false vocal cords, and from both in the greater projection anteriorly of the thyroid cartilage, as well as in the presence of a sinus which separates the false cords from the base of the epiglottis and arytaeno-epiglottidean folds of mucous membrane. Thyroid gland.-Is very small and of an elongated-oval form. It lies under cover of the sterno-thyroid muscle, and extends on each side from the middle of the cricoid cartilage down to the sixth tracheal ring. The two halves are not connected by an isthmus. Trachea.-Is 11 inches in length. It possesses 49 cartilaginous rings (according to Meckel2 53) ; individual variation may account for this difference. The rings vary very much in breadth. In the trachea of H. striata, according to Meckel, there are 45, according to Reimann3 and Wolff1 there are but 36 ; in Proteles Mr. Flower counted 36. Lungs.-The right lung is divided into 6 lobes, the left into 3. In the right lung there are two horizontal fissures, the lower of which indicates the separation between a basal lobe (which forms about one half of the lung) and the rest of the organ. The upper or apical half is divided into four lobes through the intersection of the upper horizontal by a vertical fissure. Of these, the lower and posterior lobe is almost square, and clearly separated from that above and below it, whilst the two anterior lobes are scarcely so well defined by reason of their coalescence towards the root of the organ. The sixth is the so-called azygos lobe, and lies between the upper and lower halves of the lung. The left lung is divided into an upper, a middle, and a lower lobe by means of two horizontal fissures, the inferior of which separates the lower from the upper half of the lung, whilst the upper divides the latter into two parts. Of these, the upper is the larger. On the outer surface of this lobe is a 1 Op. cit. vol. x. p. 635. a Op. cit. vol. x. p. 485. s De Hyama, Berol. 1811, p. 16. 4 De org. vocis, Berol. 1812, p. 10. |