178 DR. J. MURIE ON THE FOEM AND STEUCTUEE OF THE MANATEE. 



verge below the parotid gland and join the external jugular opposite the paramastoid. 

 The brachio-cephalic vein comes inwards from above the insertion of the pectoralis 

 minor ; and another marked tributary is derived from the vascular plexus covering the 

 inner subscapular region. 



The course of the external jugular vein is from behind the cranial end of the stylo- 

 hyal and the thereupon attached portion of the digastric muscle, backwards and slightly 

 obliquely outwards, uniting with the internal jugular near the first rib. The external 

 almost equals the internal jugular vein in calibre; and it lies over the tendon of the 

 sterno-mastoid muscle and the suprascapular artery. 



The internal jugular vein commences at the cranial aperture, foramen lacerum 

 posterius, near to the attachment of the rectus lateralis and cephalo-humeral muscles, 

 where there is a large venous plexus as in Cetacea. As it traverses the neck backwards 

 it lies chiefly to the inner side of the carotid artery, crossing it, however, about the 

 level of the bifurcation of the trachea, posterior to which it converges to the large 

 innominate trunk formed by it, the external jugular, and tlie subclavian vein. There 

 are several oblique bridging communications between the ecto- and entojugular veins. 

 No valves were observed in the above veins of the neck. 



The deep cervical glands are very voluminous, and fill the intervening cleft, bounded 

 anteriorly by the cephalo-humeral muscle, externally by the subscapularis, deeply or 

 dorsally by the short neck-muscles, the lateralis and obliquus externus, and within or 

 mesially by the extension forwards of the serratus magnus. The cervical plexus of 

 nerves passes over the glands in question, the latter being enveloped amidst the rete 

 mirabile. 



VII. Vocal and Eespiratoby Apparatus. 



1. The Air-passages. 



Stannius has been successful in his exposition of the structure of the larynx. I may 

 refer, however, to two points he and Rapp have failed to notice, viz. the existence of a 

 small recess or pseudo-sacculus laryngis at the anterior extremity of the vocal cord, as 

 in the Dugong ; and to the presence of small nodular cornicula laryngis or cartilages of 

 Santorini, surmounting the arytenoid bodies. As these authors and Vrolik state, the 

 epiglottis, unlike the Cetacean, is of the most rudimentary character ; the thyroid car- 

 tilages are united anteriorly by a narrow bridge, and anterior and posterior cornua are 

 well developed ; the cricoid is a complete ring posteriorly, very broad, and with a 

 marked prominence for the attachment of the thyroidal posterior cornu; the arytenoids 

 are trihedral; the vocal cords are the reverse of prominent, and deficient in inferior 

 excavation. The several ligaments are composed of tough yellow and fibro-elastic 

 tissues ; and the diminutive epiglottis, curiously enough, consists of like material, void 

 of a cartilage basis. 



The dozen tracheal rings, and, as fixr as I could make out, the bronchial also, are not 



