Common Frog. 185 



passes to the back of the oesophagus in close apposition with 

 the second main trunk or aorta, with which it is usually 

 connected by a ductus Botalli. 



s. Convergence of hyoglossi muscles, which, together with the 

 diverging arterial trunks, enclose a diamond-shaped space, in 

 the anterior angle of which a large glandular mass, and 

 posteriorly in which several smaller masses of similar cha- 

 racter, are lodged. Into the posterior angle of this space 

 the right auricle, which is here, as in all cold-blooded verte- 

 brata, possessed of two auricles, the larger of the two, pro- 

 trudes itself from behind the arterial trirnks. Underneath 

 these structures the recurrent laryngeal nerve passes to the 

 larynx. 



t. Thyroid proper, of which the glandular masses just spoken of 

 may be considered as divarications. It is placed just inter- 

 nally to the jugular vein. The Thymus is not seen in this 

 figure, lying far back as it does near the angle of the jaw. 

 See Ecker^s Icones Physiologicae, tab. vi., fig. 5 ; Remak, 

 Entwickelungsgeschichte der Wirbelthier, tab. viii., fig. 

 8. a. ; Kolliker, Entwickelungsgeschichte, p. 391. 



u. Left jugular vein passing down to receive the subclavian, and 

 thereby constitute the left cava of that side. 



For the continuity of the lymphatic vessels with the various serous 

 cavities of the body, see V. Recklinghausen, Handbuch der 

 Lehre von den Geweben, herausgegeben von S. Strieker, 

 ii. Lieferung, 1869, p. 223; Virchow's Archiv., 1863, Bd. 26, 

 p. 172; Dybkowsky, Schweigger-Seydel, Dogiel, and Ludwig 

 in Ludwig^s Arbeiten aus der Physiologischen Anstalt zu 

 Leipzig, 1867. 



