36 



fication of the intercostal vessels. Here again, in enunciating a 

 general anatomical propositiou regarding Cuvier's Cetacea, the her- 

 bivorous species mušt be exceptionally cited apart. 



Respiratory System. 



" The peculiar form, structure, and position of the lungs have been 

 so accurately described and figured by Raffles, Home, and Riippel, 

 that I have only to observe the olose agreement -vvith these accounts 

 ■which the structure of the parts presented in the three Dugongs dis- 

 sected by me ; Daubenton* and Humboldtf describe and figure a 

 precisely similar condition of the respiratory apparatus in the Ma- 

 natee. Steller describes the šame extension of the lungs along the 

 dorsal aspect in the Stellerus, which he aptly compares to the posi- 

 tion of the lungs in the bird, but without their fixation to the pari- 

 etės of the chest, so characteristic of that class. The Chelonian 

 reptiles, perhaps, offer a closer resemblance X to the herbivorous Ce- 

 tacea in this respect ; and it is worthy of remark that the air-cells 

 of the lungs are larger in the Dugong than in any other Mammals. 

 In the camivorous Cetacea the air-cells are remarkably minute, and 

 the lungs more compactly shaped and lodged in a shorter thorax. 



" Existing, as both the herbivorous and carnivorous Cetacea do, un- 

 der such peculiar cireumstances, — as air-breathing animals constantly 

 d\velling in an element the access of which to the lungs would be 

 immediately fatal, — it might be supposed that the mechanism of the 

 larynx, or entry to the air-passage, would be similarly modified in all 

 the species, in order to meet the contingencies of their aąuatic ex- 

 istence. But we can as little predicate a community of organization 

 in the structure of this part as of the circulating or digestive systems 

 in the Cetacea of Cuvier. The Dugong and the Dolphin present, in 

 fact, the two extremes in the Mammiferous class, in the develope- 

 ment of the epiglottis, which is one of the chief internal character- 

 istics of that class. In the true Cetacea, and the Delphinidce in par- 

 ticular, it is remarkable for its great length, while in the Dugong it 

 can hardly be said to exist at all. As the larynx, ho\vever, has only 

 been noticed cursorily in the previous anatomical accounts of the 

 Dugong, 1 beg to offer a description of this part, as it appeared 

 in the three specimens dissected. 



" The glottis is very small and presents the form of the letter T, the 

 superior transverse part of the opening being, hovvever, crescentic 

 instead of straight, Avith the horns extended a little way outside of 

 the vertical slit. This is bounded on each side by the thin convex 

 borders of the arytenoid cartilages ; the epiglottis makes a short ob- 

 tuse pyramidEd projection in front of the glottis ; on each side of this 

 projection there is a slightly-produced crescentic fold of the mucous 



* Buffon, vol. xiii. 



f Wiegmann's Arcliio fitr Natiirgeschichte, 1838, pi. ii. fig. .5. 



+ This resemblance is iurtlier eNcmpliiied in the shortness of the trachea, 

 the completeness of its cartilaginoiis rings, the length of the bronchial tubes, 

 and the extension of their cartilaginous structure far into the substance of 

 the lungs in the Dugong. 



