16 THE GREASE, 



harbour dirt, but, on the contrary, prevents its 

 access to the limb, it will be no difficult task to 

 shew its utility. 



Nature has cloathed the animal with hair 

 for the obvious purpose of defending the skin 

 from the contact of the atmosphere. Other 

 membraneous parts, such as the nostrils and the 

 eyes, are shielded, with the same intention, by 

 peculiar secreted fluids, which in a state of 

 health constantly cover their surfaces. The in- 

 ward surface of the nostrils is kept moist, in 

 •order to preserve the sense of smelling ; and the 

 outward surface of the eye is kept moist, in or- 

 der to preserve its transparency. 



Both of these faculties would be destroyed 

 by the contact of atmospheric air, which, by 

 drying the surface of the nostril, would render 

 it incapable of smelling ; and which also, by 

 drying the surface of the eye, would corrugate 

 «t, and render it opaque by the multiplicity of 



refractions 



