LUNGS OF MAMMALIA. 581 



lap each other : the tracheal muscles are attached to their inner 

 surface at the angle where the free ends are bent inwards. The 

 lungs are, as in Rhinoceros, each somewhat notched where they 

 embrace the pericardium. The left lung, in the Tapir, has, be- 

 sides the fissure opposite the base of the heart, a second nearer 

 the apex. The right lung is more definitely three-lobed, the 

 lower one forming the azygous process. The tracheal rings are 

 thick and broad, as in the Rhinoceros. 



In Strides and Camelidce the left lung is rarely cleft so as to 

 show two lobes : the right is more commonly so, with the ' lobulus 

 impar ' as a process of the lower lobe. In the Wart-Hog {Pha- 

 cochoerus) and Hippopotamus an upper lobe is distinguishable 

 from a lower one, in the left lung, and the right shows three 

 lobes, besides the lobulus impar. In the Ruminants it is more 

 common to find three lobes on the left side and four, including 

 the azygos one, on the right. The chief peculiarity of the respi- 

 ratory system in the Ruminant group relates to the length of the 

 neck, with which the windpipe is made to agree by the number 

 not the length of its rings : thus the Camel may have upwards 

 of 100 rings, the Giraffe upwards of 90, the Llama 80, while the 

 shorter-necked Musks have not more than 50 tracheal rings. In 

 some Ruminants the right bronchus bifurcates at its origin, and 

 the left seems a third tube. The tracheal rings are cleft poste- 

 riorly, with the ends touching or overlapping. 



In certain pinnigrade Carnivora the tracheal rings are entire for 

 some way down the tube, and in the cleft rings the ends overlap. 

 Phoca vitulina has upwards of 70 rings. I found the left lung 

 in this Seal rather larger than the right, and both divided into 

 two lobes : Hunter noted three lobes on the left side ' united by 

 a loose cellular texture.' l In the Ursine Plantigrades the left 

 lung has two lobes, the right three and the lobulus impar. The 

 tracheal rings are thickest anteriorly, thinning off to their edges 

 at the posterior cleft : there is a slight alternate overlapping, or 

 interlocking, both in successive rings, and at the fore and back 

 parts of the same ring. 



The Ratel, Wolverine, and Carcajou, agree with the Bears in 

 the pulmonary divisions : the Mydaus has three lobes to the lung ; 

 and the lobulus impar of the right lung is large and notched. 

 In the Otter the left lung has two lobes and the right four lobes 

 including the lobulus impar: the ends of the cleft tracheal 

 rings are thinned off and overlap more closely than in terrestrial 

 Carnivora, The tracheal tube is wide in most of the order, the 

 number of rings ranges from 40 to 60. In Digitigrades as a rule 

 1 ccxxxvi. vol. ii. p. 96. 



