TYPES OF CONSTRUCTION. 77 



necessity," as Newton called Fate and Nature without 

 God, could certainly produce no such " variety of things " 

 as we see here, while the unity pervading the functional 

 character of the different organs is plain enough proof 

 of their being the work of the same Artisan. 



Various functions are attained by a modification of 

 similar structure. Thus the simplest plant differs from 

 the most complex principally in this that the whole 

 external surface of the former participates equally in all 

 the operations which connect it with the external world, 

 as those of Absorption, Exhalation, and Respiration, 

 while in the latter these functions are confined to certain 

 parts of the surface. So in the highest animals, the or- 

 gans adapted to the functions of Absorption, Exhala- 

 tion, Respiration, Secretion, and Reproduction, are all 

 composed essentially of a membrane which is a prolonga- 

 tion of the general surface, while this general surface is 

 the sole instrument for the performance of these func- 

 tions in the lowest animals, and shows no special adap- 

 tation for one or another of them. So that it may be 

 expressed as a general truth of Biology, that " through- 

 out all animate Creation, the functional character of the 

 organs which all possess in common, remains the same ; 

 while the mode in which that character is manifested 

 varies with the general plan upon which the being is 

 constructed."* 



In all living things the attainment of function is the 

 cause of modification of structure. This gives evidence 

 of Creative plan, or design, in direct opposition to the 

 theory of gradual evolution of structure, and is proof also 



* Carpenter's "General and Comparative Physiology." 



7* 



