92 NATURAL THEOLOGY. 



A single secretion being wrong is enough to make 

 life miserable, or sometimes to destroy it. Nor is 

 the variety less than the importance. From one 

 and the same blood, (I speak of the human body,) 

 about twenty different fluids are separated ; in 

 their sensible properties, in taste, smell, colour, 

 and consistency, the most unlike one another that 

 is possible ; thick, thin, salt, bitter, sweet : and if 

 from our own we pass to other species of animals, 

 we find amongst their secretions not only the most 

 various but the most opposite properties ; the most 

 nutritious aliment, the deadliest poison ; the sw^eet- 

 est perfumes, the most foetid odours. Of these 

 the greater part, as the gastric juice, the saliva, 

 the bile, the slippery mucilage which lubricates 

 the joints, the tears which moisten the eye, the 

 wax which defends the ear, are, after they are 

 secreted, made use of in the animal economy, are 

 evidently subservient, and are actually contribut- 

 ing to the utilities of the animal itself. Other 

 fluids seem to be separated only to be rejected. 

 That this also is necessary (though why it w^as 

 originally necessary we cannot tell,) is shown by 

 the consequence of the separation being long sus- 

 pended, which consequence is disease and death. 

 Akin to secretion, if not the same thing, is assimi- 

 lation, by which one and the same blood is con- 

 verted into bone, muscular flesh, nerves, mem- 

 branes, tendons ; things as difterent as the wood 

 and iron, canvass and cordage, of which a ship 

 with its furniture is composed. We have no ope- 



