THE PROCESS OF REPRODUCTION. 455 



ing and vitalizing the different elementary substances. It is impos- 

 sible to imagine that this organizing agency of the stomach tan be 

 chemical. This agency is vital, and its nature completely unknown." 



CHAPTER IV. 



EXAMINATION OF THE PROCESS OF REPRODUCTION IN ANIMALS AND 

 PLANTS, AND CONSEQUENT SPECULATIONS. 



Sect. i. The Examination of the Process of Reproduction in 



Animals. 



IT would not, perhaps, be necessary to give any more examples of 

 what has hitherto been the general process of investigations on 

 each branch of physiology ; or to illustrate further the combination 

 which such researches present, of certain with uncertain knowledge ; 

 of solid discoveries of organs and processes, succeeded by indefinite and 

 doubtful speculation concerning vital forces. But the reproduction of 

 organized beings is not only a subject of so much interest as to require 

 some notice, but also offers to us laws and principles which include 

 both the vegetable and the animal kingdom ; and which, therefore, are 

 requisite to render intelligible the most general views to which we can 

 attain, respecting the world of organization. 



The facts and laws of reproduction were first studied in detail in 

 animals. The subject appears to have attracted the attention of some 

 of the philosophers of antiquity in an extraordinary degree : and indeed 

 we may easily imagine that they hoped, by following this path, if any, 

 co solve the mystery of creation. Aristotle appears to have pursued it 

 \vith peculiar complacency ; and his great work On animals contains 1 

 an extraordinary collection of curious observations relative to this sub- 

 ject. He had learnt the modes of reproduction of most of the animals 

 with which he was acquainted ; and his work is still, as a writer of our 

 own times has said,* " original after so many copies, and young after 

 two thousand years." His observations referred principally to the 

 external circumstances of generation : the anatomical examination was 



1 Bourdon, p. 161. 2 Ib. p. 101. 



