74 
ANATOMY AND PHYSIOLOGY 
alkali; nor is the animal part so transparent when 
deprived of the earth. 
efi The bones are less compact than those of quad- 
rupeds that are similar to them. Their form somewhat 
resembles what takes place in the quadruped, at least in 
those whose uses are similar ; as the vetebrse, ribs, and 
bones of the anterior extremities, have their articulation 
alike, though not in all of them. The articulations of 
the lower jaw of the carpus, metacarpus, and fingers, are 
exceptions. The articulation of the lower jaw is not by 
simple contact, either single or double, joined by a cap- 
sular ligament, as in the quadruped, but by a very thick 
intermediate substance of the ligamentous kind, so inter- 
woven that its parts move on each other, in the inter™ 
slices of which is an oik This thick matted substance 
may answer the same purpose as the double joint in the 
quadruped, 
“ The two fins are analogous to the anterior extremi- 
ties of the quadruped, and are also similar in construction. 
A fin is composed of a scapula, os humeri, ulna, radius, 
carpus and metacarpus, in which last may be included the 
fingers, because the number of bones are those wdiicli 
might be called fingers, although they are not separated, 
but included in one general covering with the meta- 
carpus. They have nothing analogous to the thumb, 
and the number of bones in each is different ; in the 
forefinger there are five bones, in the middle and ring 
fingers seven, and in the little finger four. 
“ The articulations of the carpus, metacarpus, and 
fingers, are different to those of the quadruped, not 
