THE CELL DOCTRINE. 107 



proves that the whole suhstance of the nettle is made 

 up of a repetition of such masses of nucleated proto- 

 plasm, each contained in a wooden case, which is 

 modified in form, sometimes into a woody fibre, 

 sometimes into a duct or spiral vessel, sometimes 

 into a pollen grain, or an ovule. Traced back to its 

 earliest state, the nettle arises as the man does, in a 

 particle of nucleated protoplasm. And in the lowest 

 plants, as in the lowest animals, a single mass of such 

 protoplasm may constitute the whole plant, or the 

 protoplasm may exist without a nucleus. Under 

 these circumstances it may well be asked, how is one 

 mass of non-nucleated protoplasm to be distinguished 

 from another ? why call one ' plant,' and the other 

 ' animal ?' The only reply is that, so far as form is 

 concerned, plants and animals are not separable, and 

 that, in many cases, it is a mere matter of conven- 

 tion whether we call a given organism an animal or 

 a plant." 



The researches of the chemist have also shown a 

 like uniformity of chemical composition in " proto- 

 plasm " or living matter, proving that whatever its 

 source, it contains carbon, hydrogen, oxygen, and 

 nitrogen, producing in their combination a complex 

 substance, which in our ignorance of its more exact 

 nature, we call proteinaceous or albuminoid matter. 



Further, the matter of life is composed of ordi- 

 nary matter, and again resolved into ordinary matter 

 when its work is done. Waste is constantly going 

 on, which must be supplied by food, which is con- 

 verted into protoplasm. A solution of smelling salts 

 in water, with an infinitesimal proportion of some 



