70 CLASS MAMMALIA. 



strous, either from an excess or a deficiency of the sub- 

 stance which composes them. Castration will arrest their 

 expansion, and dry up the source which gave them ex- 

 istence ; a wound will give another direction to the vessels, 

 and in this manner produce branches where none would 

 appear otherwise. If in this case one horn becomes mon- 

 strous from excess, the other will be so from a defect of 

 substance : to conclude, advanced age has also its influence, 

 the horns then become small, slender, and, finally, irregular. 

 The flattened or palmated shape of the horns in several 

 species, seems to be a provision of nature to enable the 

 animals to clear the snow off their food, for it is remark- 

 able that this structure is confined to those of the higher 

 latitudes, and rendered applicable in proportion as they 

 inhabit more rigorous climates. Thus, in the Rein-deer, 

 who are absolutely arctic, it is most so, and least in the 

 Fallow-deer, who belong to the colder temperate regions. 

 This form is to be traced even in some of the AntilopinEe of 

 America, Dicranocerus Palmatus, who resides the furthest 

 north, bearing horns much broader than the next species 

 D. Furcifer. The Caribous of America, who have to con- 

 tend still more with deep snow than the Rein-deer of the 

 old continent, have their horns broader and better adapted 

 to that purpose ; besides, both varieties, in addition to 

 these natural shovels, have broad feet, not only to sustain 

 them the better on snow, but also to clear it away. Thus 

 these arctic inhabitants are provided with a double orga- 

 nization for this purpose, while others less northerly rumi- 

 nants have only one provision ; as the horns of the Elk, or 

 the feet of Ovibos and Aplocerus Lanigerus ; these, besides, 

 migrate to latitudes of a milder character. The horns of 

 the Rein-deer, indeed, drop in winter, but this takes place 

 only at a period when the snow is already not only very 

 deep, but frozen hard, and even then we see, that the 

 females, when gravid, and therefore in want of a greater 



