CONCLUSION. 123 



rate such matter from the inorganic substances 

 around them, as is then, and not till then, ca- 

 pable of affording him the sort of food he needs, 

 whether derived directly from the plants them- 

 selves, or furnished by them indirectly through 

 the animals they support, and on whom he de- 

 pends for nutriment. Who can look on the 

 principal constituents of plants, i. e. carbon, 

 oxygen, hydrogen, and nitrogen, and contem- 

 plate their gradual transformation into vegetable 

 albumen, and vegetable caseine,* or on any of 

 the elementary forms of the nitrogenized com- 

 pounds, so absolutely essential, directly or indi- 

 rectly, to animal life, without feeling that no- 

 thing stands alone in this world, but that " the 

 chain holds on, and where it ends, unknown." 

 And even should it also occur to the mind, that 

 the same process ceases not with us, but that 

 these human bodies, thus marvellously made 

 and nourished, are, even the organs by which 

 the high functions of the brain are performed, 

 material and perishable, and that " we feed our- 

 selves to feed the worms," and, being dust, re- 

 turn literally to that dust again ; let us not 

 pause on the threshold of the argument, where 



* " Introduction to Organic Chemistry," p. 33. 



