THE HAIR AND FUR OF ANIMALS. 145 



If this fur had been strong, as in the rat or 

 mouse, in these retreats for life it would have 

 doubly retarded the progress of the creature; first 

 by its resistance, and then acting as a brush, so as 

 to choke up the galleries, by removing the loose 

 earth from the sides and ceilings of the arched ways ; 

 thus impeding at least, if not absolutely preventing, 

 retreat ; but the softness of the fur obviates both 

 these fatal effects. 



The construction of the hair and fur of different 

 creatures is very various and beautiful ; and, if we 

 believe in the beneficence of the All- wise Creator, 

 we must conclude that such peculiar fabrications 

 were resorted to for the 'purpose of being imme- 

 diately useful, or as necessary to the condition of 

 the animal. In a mere sketch like this, it would 

 conduct me infinitely beyond my intentions to enu- 

 merate the many varieties of hair that are rendered 

 manifest by the microscope ; but three or four may 

 be mentioned. The fur or clothing of the mole 

 (Plate 3, Fig. 4, A) is internally composed of col- 

 lateral bars. In man the hairs have at times a cen- 

 tral tube, for the conveyance of medullary matter, 

 as in bones, or some nutriment analogous to it ; 

 but in the mole there appears to be no communi- 

 cation with the body of the animal, unless the per- 

 spirable matter is conducted alternately from side 

 to side along the bars. The fur of the bat (Fig. 

 B) has knots like the rudiments of branches. The 

 hairs of the hamster mouse (Fig. C) have a central 

 perforation, apparently uninterrupted throughout 



