348 DISTINCTION BETWEEN PLANTS AND ANIMALS. 



ric is constructed, is a neutral ternary product (27, 347), com- 

 posed of carbon, hydrogen, and oxygen. Although the plant ne- 

 cessarily contains and produces the quaternary organic products, 

 these do not enter into the composition of its permanent fabric. 

 The animal tissue, on the contrary, is directly composed of neutral 

 quaternary products, consisting of carbon, hydrogen, oxygen, and 

 nitrogen. Although such distinctions as these are, in all probabil- 

 ity, absolute, yet it is often difficult, and frequently, perhaps, im- 

 possible, to apply them to the actual discrimination of the lower 

 plants from the lower animals. 



