74 Dr. Harwood on the Structure and 



would produce the same efFect) do the auricles of the seal com- 

 municate, as was formerly thought. On the contrary, in the 

 seal the original type in the construction of the heart is still 

 retained, as also in the walrus and otter, and other aquatic 

 mammalia, with this exception, — that the veins which return the 

 blood to the heart are so much enlarged, that they are capable 

 of changing their office, and becoming reservoirs for receiving 

 and retaining the blood in its progress to the heart. Thus is 

 the right side of the latter, and the lungs, prevented from being 

 oppressed by its superabundance when the creature is under 

 water, and incapable of breathing, and thus is its life sus- 

 tained. The largest of these venous reservoirs exists in the 

 liver of the seal ; but its whole venous system, like that of the 

 walrus and the whales, is very greatly developed. If I may 

 be allowed the expression, like most other aquatic mammalia, 

 the seal appears to be literally gorged with blood ; its blood is 

 moreover of an unusually dark colour, being almost black, 

 which property it perhaps acquires by its constant liability to 

 become arrested in its course ; and hence, perhaps, the neces- 

 sity for so much blood in its circulating system — ^yet the animal 

 heat of the seal is very great. 



We shall next briefly advert to some of the senses of this 

 animal. Its very large and dark eyes being directed more for- 

 wards than in any other aquatic quadruped, added to the round 

 and human appearance of its head, when raised above the 

 surface of the water, doubtless caused it to contribute greatly 

 towards the formation of those ideal marine monsters of which 

 the ancients have favoured us with so many accounts. The eye 

 of the seal is provided with a most perfect membrana nictitans, 

 or winking membrane, the use of which it is rather difficult to 

 conceive in aquatic animals, except to shield their delicate 

 organs from the too powerful effects of the light, in rapidly 

 rising from the depths to the surface. The pupil of the seal is 

 vertical, like that of the Cat ; but its soft expressive phy- 

 siognomy, which more nearly resembles that of the dog than 

 any other quadruped, and is equally expressive of superior in- 

 telligence, is not affected by the cat-like form of the pupil, in 

 consequence of the dark colour of the iris. But the greatest 

 peculiarity in the construction of its eye, is a narrow zone, or 



