258 ZOOLOGICAL PHILOSOPHY 



of living bodies incessantly builds up combinations, which would not 

 have arisen without it : but I shall again repeat that if it is true, as 

 can hardly be doubted, that all compound mineral substances such as 

 earths and rocks, and all metallic, sulphurous, bituminous, saline 

 substances, etc., arise from the remains of living bodies, — remains 

 which have undergone successive decompositions on and under the 

 surface of the earth and waters ; it is equally true to say that living 

 bodies are the original source from which all known compound sub- 

 stances have arisen. (See my Hydrogéologie, p. 91 et seq.) 



It would thus be a vain task to try to make a rich and varied collection 

 of minerals in certain regions of the earth, such as the vast deserts 

 of Africa, where for many centuries there have been no plants and only 

 a few stray animals. 



Now that I have shown that living bodies form their own substance 

 for themselves as well as the various matters that they secrete, I must 

 say a word about the faculty of feeding and growing which all these 

 bodies possess within certain limits, since these faculties again are 

 the result of vital activities. 



