552 DE. J. MUEIE OX THE AX ATOMY OF THE SEA-LIOX. 



given forth by a weaker and more metallic voice than is possessed by the adult male 

 Sea-lion. 



In the trachea the uppermost cartilaginous rings are wide and subequal ; they do not 

 meet behind, the interspace being occupied by membrane. Moreover a dense layer of 

 fibro-elastic tissue unites the trachea to the gullet, and, passing over both, ensheaths the 

 thyroid gland and the vessels and nerves distributed thereabouts. This strong mem- 

 branous investment or layer of deep cervical fascia appears to contain much yellow 

 elastic fibre in its composition, and while surrounding the trachea tends powerfully to 

 bring the cartilaginous rings together, a needful provision to the remarkable flexible 

 neck of the creature. 



b. Lungs. — The lungs have great capacity, and when inflated are unusually long in 

 shape. In this respect they correspond to the form of the very mobile thoracic walls. 

 As has been previously mentioned, the Sea-lion alters remarkably in the rotundity, 

 length, depth, and flatness of its body, according as the animal walks on all fours, 

 swims, or lolls on the ground. This plasticity of the chest is due chiefly to the loose 

 manner in which the ribs are articulated to the bodies of the vertebrae, and also to the 

 amount of intervertebral, costal, and sternal cartilages present, all more or less acted 

 upon by the large thoracic muscles. 



The right lung rises slightly highest in the chest. It is divided into four lobes, or is 

 composed of three considerable-sized lobes and the so-called lobulus impar, in this case 

 tolerably free. The upper or anterior lobe is of a trihedral form, and rather flattened 

 at the edges ; the lower angle descending and covering the right side of the root of the 

 heart. Its lower margin is slightly concave at the posterior third, allowing the bron- 

 chus and the second lobe to fit into the hollow. This upper or anterior lobe has a 

 separate or third bronchial division, which is derived from the usual right bronchus 

 6 inches below the bifurcation of the trachea. The second or middle lobe of the right 

 lung is long, narrow and spatulate. The third inferior (posterior) lobe is the thickest 

 and slightly larger than the anterior or first lobe ; it is triangular in shape. The fourth, 

 or lobus impar, is derived from the cardiac side of the root of the last, but receives a 

 separate extension of the right bronchus, so that it forms an individual lobe. Single 

 and pedunculate at the base, it divides distally in a trefoil manner, each spur being 

 three-sided. 



The left lung is composed of three main lobes : the first one is deeply cleft at its 

 uppermost corner. The second, middle, smaller one is attached to the lower end of the 

 first ; it is short, narrow, flat and broad at the free extremity. The third lobe is the 

 largest of all ; it is triangular, the upper margin being slightly concave. The sternal 

 free margins of all the lobes of both lungs have an irregular somewhat ci - enated border ; 

 this is most notable in the middle, spatulate lobes. 



c. Glands in proximity to Air-passages. — The thyroid bodies, relatively to the size of 

 the animal, are small. They are situated widely apart, without any connecting isthmus, 



