DESCRIPTION bt 
easily determine the sex of a beaver, except in the case of 
adult females, which have four teats, two between the fore 
legs, and two three inches farther back. 
There are two pairs of large glands under the skin in 
front of the rectum. ‘The anterior and larger pair of these 
are the castoreum sacs, containing castoreum, and the 
smaller, posterior pair are the oil sacs. More will be said 
about the castoreum later. 
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