480 



CARNIVORA. 



an adult seal, in which both these channels of 

 communication remained open ; and the writer 

 of this article dissected a seal some years since 

 which was nearly full grown, in which the 

 foramen ovule was so open as to allow the 

 tip of the little finger to enter, and the ductus 

 arteriosus would admit with ease the bulb of a 

 common probe. 



Upon the whole then it appears that, al- 

 though the pervious condition of these chan- 

 nels cannot be considered as general in the 

 adult state of these diving animals, as has 

 sometimes been supposed, it must be allowed 

 that this exception is far more frequent in them 

 than in any other mammiferous animals, and 

 that, as a general rule, these holes remain open 

 later in such animals than in others. There is, 

 however, in the otters and in the seals, a con- 

 siderable dilatable enlargement observed in the 

 inferior cava, which serves doubtless as a re- 

 servoir to retain part of the returning blood 

 during submersion, until the animal rises again 

 to breathe. 



Organs of respiration. The lungs are di- 

 vided into lobes varying but little in number 

 in the terrestrial families of the order. These 

 all have four lobes to the right lung, and either 

 two or three to the left. The seals have the 

 right lung divided into two lobes, and the left 

 undivided. 



The cartilaginous portions of the rings of 

 which the trachea is composed vary in the 

 proportions which these bear to the whole 

 circle ; in the genus Mustela and some others, 

 the cartilage forms about two-thirds of the 

 circle; in the bear, the coati, and the cats, 

 about three-fourths ; and in the ichneumon as 

 much as four-fifths. 



The nervous system. On viewing the dif- 

 ferent orders of mammij'era in the ascending 

 series, the brain of the Carnivora (Jig. 201 

 being an upper and a lateral view of that of the 

 Lion) will be found to exhibit a higher degree 



Fig. 201. 



just mentioned,) instead of the labyrinthine 

 duplicatures which are observable in the Qua- 

 drumana and in man, are, generally speaking, 

 longitudinal in their direction, the principal 

 being but two on each side of the median line, 

 crossed by a transverse anterior one. The 

 cerebellum is almost wholly uncovered as seen 

 from above, not more than one-fifth of it lying 

 under the posterior edges of the hemispheres. 

 The optic thalami, however, are concealed not 

 only from above but even on a lateral view, 

 by the hemispheres. Of the tubercula qua- 

 drigemina, the posterior are the larger. 



The eye possesses but few peculiarities of 

 any importance. The relative proportions of 

 the different humours are here more nearly 

 equalized than in any order of the mammalia, 

 at least in some of the genera, as the following 

 comparative view will shew : 



Dog 

 Man 

 Ox 



Aqueous. 



Crystalline. 

 2T 



Vitreous. 



51 

 . f | 



- if 



of developement than exists either in the 

 cetacea, in any of the forms of the herbivora, 

 or in the marsupiata ; the hemispheres have 

 here a well-marked superiority of develope- 

 ment over the cerebellum and tubercula quadri- 

 gemina. On the other hand the brain of the 

 Carnivora is less developed anteriorly than in 

 the Quadrumana, the anterior lobes being some- 

 what narrowed and depressed, and the con- 

 volutions, (although deeper than in the orders 



The vitreous humour, therefore, is much less 

 than in either of the other cases, and the crys- 

 talline smaller in proportion than that of man. 

 The crystalline lens in the Seal fulfils the gene- 

 ral law which gives to it a degree of sphericity 

 in relation with the aquatic habits of the 

 animal. Thus the crystalline of fishes is ab- 

 solutely spherical, that of the cetacea nearly so, 

 and that of the seal and of the otter very much 

 less flattened than in those animals which re- 

 side and seek their food on land. In the seal 

 also the sclerotic is considerably thickened 

 anteriorly and still more dense at the posterior 

 part, whilst the middle zone is very thin and 

 flexible, a structure which must offer great 

 facility for the action of the different muscles 

 which compress the globe, and alter the rela- 

 tive proportion of its diameter to its axis. The 

 form of the pupil differs in different groups. 

 In the diurnal carnivora, and even in some 

 nocturnal, it is permanently round ; but in the 

 cats it is perpendicular during its contracted 

 state, and in a very bright light it is almost 

 linear, but even in these it becomes perfectly 

 round in the dark, and the ellipse which it 

 forms in its contraction is more or less length- 

 ened or acute according to the degree of light. 

 The inner surface of the choroid is partially 

 lined with a brilliant greenish tapetum, similar 

 to that which is found in the ruminantia, and 

 occupying nearly the same situation. 



The lachrymal gland exists throughout this 

 order, and the glandula Harderi is also found 

 in its members as well as in the ruminantia, 

 pachydermata, and some if not all the ro- 

 dent ia. 



The organ of hearing is developed to a very 

 considerable degree in most of the Carnivora. 

 The external ear varies much in size and form; 

 it is moderate in the cats, small in the bears, 

 and rudimentary in the seals, but enormously 

 large in the Fennec, a species of the family 

 Canute. There is in these, as well as in many 

 other mammiferous animals, especially the ro- 

 dcntia, a remarkable hollow appendage to the 



