20 THEORIES OF LIFE, [iNTKOD. 



ence of circumstances affecting the parents, as is proved both in the 

 animal and vegetable kingdoms in the production of hybrids. "Two 

 distinct species of the same genus of plants," says Dr. Lindley, "will 

 often together produce an offspring intermediate in character be- 

 tween themselves, and capable of performing all its vital functions 

 as perfectly as either parent, with the exception of its being unequal 

 to perpetuating itself permanently by seed ; should it not be abso- 

 lutely sterile, it will become so after a few generations. It may, 

 however, be rendered fertile by the application of the pollen of 

 either of its parents ; in which case its offspring assumes the cha- 

 racter of the parent by which the pollen was supplied." The same 

 thing precisely occurs among animals, and the mixed offspring, or 

 mule, produced by the union of different species, is incapable of 

 breeding with another mule ; but not so with an animal of the same 

 species as either of its parents. How entirely inadequate is the 

 theory of organic agents to explain these occurrences ; it cannot, 

 surely, be maintained that a mixed organic agent is produced from 

 the conjunction of the organic agents of the dissimilar species to 

 direct the formation of this mixed organism ! 



The remarkable fact, that the various tribes of the human race, 

 dissimilar as they are, were derived from the first created pair, may 

 be adduced as a striking illustration of the influence of physical 

 agency in modifying organic development. The most potent cause 

 of these changes has been climate; but particular customs and 

 usages, connected with the uncivilized state, have not been without 

 their influence. Climate also produces considerable modifications in 

 the size and other characters of the lower animals. Sturm affirms 

 that cattle transported from the temperate zones of Europe (Hol- 

 land or England), to the East Indies, become considerably smaller 

 in their succeeding generations. 



The theory of organic agents affords no more satisfactory expla- 

 nation of disease, or of death. In both cases the organic agent 

 must be at fault ; for as it is the sole guide and controller of the 

 organizing process, so it is not to be supposed that anything can go 

 astray, except under its guidance. And yet it seems impossible to 

 imagine that the ordinary causes of disease could affect such an 

 entity. On the other hand, any physical or mental cause, general 

 or local, affecting the substance of which the body is composed, 

 may so alter and modify the affinities of its particles as to occasion 

 a material disturbance in their actions ; and it is not difficult to 

 conceive that this disturbance may be of such a kind as to put a 

 stop to vital action immediately or remotely. 



