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ANATOMY AND PHYSIOLOGY 
amazing strength to this part. The substance of the 
tail is so firm and compact that the vessels retain their 
dilated state even when cut across, and this section 
consists of a large vessel surrounded by as many small 
ones as can come in contact with its external surface ; 
which of these are arteries and which veins, I do not 
knowc The fins are merely covered with a strong con- 
densed adipose membrane. 
OF THE SKIN. 
The covering in this order of animals consists of a 
cuticle and cutis ; the cuticle is somewhat similar to that 
on the sole of the foot in the human species, and 
appears to be made up of a number of layers which 
separate by slight putrefaction, but this I suspect arises 
in some degree from there being a succession of cuticles 
formed. It has no degree of elasticity or toughness, 
but tears easily, nor do its fibres appear to have any 
particular direction. The internal stratum is tough 
and thick, and in the spermaceti whale its internal 
surface when separated from the cutis is just like velvet, 
each pile standing firm in its place, but this is not so 
distinguished in some of the others. 
It is the cuticle which gives the colour to the animal ; 
and in parts that are dark, I think I have seen a dirty 
coloured substance washed away in the separation of the 
cuticle from the cutis, which must be a kind of rete 
mucosum. 
The cutis in this tribe is extremely villous on its 
