208 SYMB10GENES1S 



to such a degenerate organism that the term "quasi- 

 mechanical " should be applied. Such is the frailty of 

 organic life that under temptations it is apt to sink to a quasi- 

 mechanical level where a biologically negative (merely 

 mechanical) resultant tends to obtain predominance at the 

 expense of a purposive (symbiotic) resultant and pathological 

 conditions consequently become dominant. 



Spencer concedes in a general way that it is the funda- 

 mental difference of character between plant and animal which 

 produces the great chemical contrasts between those comple- 

 ments in the great synthesis of life. 



We have next to note, as having here a meaning for us, the chemical 

 contrasts between those organisms which carry on their functions by 

 the help of external forces, and those which carry on their functions 

 by forces evolved from within. If we compare animals and plants, we 

 see that whereas plants, characterised as a class by containing but little 

 nitrogen, are dependent on the solar rays for their vital activities ; 

 animals, the vital activities of which are not thus dependent, mainly 

 consist of nitrogenous substances. There is one marked exception to 

 this broad distinction, however; and this exception is specially instruc- 

 tive. Among plants, there is a considerable group the Fungi many 

 members of which, if not all, can live and grow in the dark ; and it is 

 their peculiarity that they are very much more nitrogenous than other 

 plants. Yet a third class of facts, of like significance, is disclosed when 

 we compare different portions of the same organisms. The seed con- 

 tains nitrogenous substance in a far higher ratio than the rest of the 

 plant; and the seed differs from the rest of the plant in its ability to 

 initiate, in the absence of light, extensive vital changes, the changes 

 constituting germination. Similarly in the bodies of animals, those 

 parts which carry on active functions are nitrogenous ; while parts that 

 are non-nitrogenous as the deposits of fat carry on no active functions. 

 And we even find that the appearance of non-nitrogenous matter, 

 throughout tissues normally composed almost wholly of nitrogenous 

 matter, is accompanied by loss of activity : what is called fatty degenera- 

 tion being the concomitant of failing vitality. 



It is thus clear again that, in spite of all temptations to 

 the contrary, plant and animal have in the main and for aeons 

 of time steadily kept on their respective paths, have through- 

 out obeyed a definite biological law, viz., that of symbio- 

 genesis, have avoided short cuts and in particular the dangers 



