RODENTIA. 133 
spoken, but of which several still have well developed clavicles. Of this 
number is the 
Castor, Lin. 
The Beavers are distinguished from all other Rodentia by their hori- 
zontally flattened tail, which is nearly of an oval form, and covered with 
scales. They have five toes to each foot: those of the hinder ones are 
connected by membranes, and that next to the thumb has a double and 
oblique nail. Their grinders, to the number of four throughout, and 
with flat crowns, appear as if formed of a bony ribbon reflected on itself, 
so as to shew one sloping edge at the internal border and three at the ex- 
ternal one of the upper row; in the lower ones it is exactly the reverse. 
Beavers are large animals, whose life is completely aquatic; their feet 
and tail aid them equally well in swimming. As their chief food is bark, 
and other hard substances, their incisors are very powerful, and grow as 
rapidly from the root as they are worn away at the point. With these 
teeth they cut trees of every description. 
Large glandular pouches which terminate on the prepuce produce a 
highly odorous oily substance, employed in medicine under the name of 
Castor (a). The organs of generation in both sexes terminate in the ex- 
tremity of the rectum, so that there is but a single external opening. 
C. fiber, Buff. VIII. xxxvi. (The Beaver). Larger than the 
badger, and of all quadrupeds the most industrious in constructing a 
dwelling, to effect which these animals act in concert in the most 
solitary parts of North America. 
Beavers choose water of sufficient depth to be frozen to the bot- 
tom, and as far as possible, running streams, in order that the wood 
which they cut above may be carried downwards by the current to 
the spot where it is to be used. They keep the water at an equal 
height, by dams composed of all sorts of branches, mixed with clay 
eS" (a) The pouches of the beaver here alluded to are found in both sexes, being 
situated in the male behind the prepuce, and in the female at the upper edge of the 
orifice of the vagina, where they open. They are composed of dense cellular tissue, 
forming several folds, between which the castor is inclosed, and to which it adheres. 
The two pouches lie parallel with each other beneath the skin; they hang together, 
and separate a little at one of the extremities, which is larger and more rounded than 
the other. Their outer surface is smooth, of a dark brown colour, and free from 
hairs. The castor completely fills the pouches, but has a cavity in the centre, which 
is a distinguishing character that shews the genuine from the artificial article. When 
examined in the animal, the secretion is soft, being of a consistence somewhat in- 
termediate between wax and honey; but, when taken out, it dries, but does not be- 
come hard. The best castor used to come from Russia, in roundish, solid pods, 
smooth on the outside, and, when cut, presenting an orange-coloured surface. At 
present, the chief portion imported into this country is from Canada; it is brought in 
thin oblong pods, which are corrugated on the outside, and the castor contained in 
them is more deeply coloured than the Russian. Castor has a very peculiar, strong, 
and disagreeable odour; its taste is bitter, acrid, and slightly aromatic. Chemistry 
has discovered in castor a variety of substances, of which castorine is the principal. 
Castor is employed in medicine as a powerful antispasmodic in hysteric cases, and 
its effect is described by physiologists as being specifically applied to what are called 
the cerebro-spinal nerves, or those which have a mixed origin from the brain and 
spinal marrow. When taken, even to a small extent, it manifests its influence in 
the urine by its very peculiar flavour; but its efficacy as a remedy has considerably 
fallen in credit.— ENG. Ep. 
