PHYSIOLOGICAL CONSIDERATIONS. 



ON THE REPRODUCTION OF ORGANIZED 



BEINGS.* 



" If the changes which living beings un- 

 dergo during the period of their existence, 

 and the termination of that existence by 

 the separation of their elements at a period 

 more or less remote from their first combina- 

 tion, be regarded as distinguishing them in 

 a striking and evident manner from the 

 masses of inert matter which surround them, 

 still more is their difference manifested in 

 the series of processes which constitute the 

 function of Reproduction. A very unneces- 

 sary degree of mystery has been spread 

 around the exercise of this function, not 

 only by general inquirers, but by scientific 

 physiologists. It has been regarded as a 

 process never to be comprehended by man, 

 of which the nature and the laws are alike 

 inscrutable. A fair comparison of it, how- 

 ever, with other functions, will show that it 

 is not in reality less comprehensible or more 

 recondite than any one of them; — that our 

 acquaintance with each depends upon the 

 facility with which it may be submitted to 

 investigation ; — and that, if properly in- 

 quired into by an extensive survey of the 

 animated world, the real character of the 

 process, its conditions, and its mode of oper- 

 ation, may be understood as completely as 

 those of any other vital phenomenon. 



" It may be considered as a fundamental 

 truth of Physiological Science, that every 

 living organism has had its origin in a pre- 

 existing organism. The doctrine of ' spon- 

 taneous generation,' or the supposed origina- 

 tion of organized structures de novo out of 

 assemblages of inorganic particles, although 

 at different times sustained with a consider- 



* Carpenter's Physiology. 



able show of argument, based on a specious 

 array of facts, cannot now be said to have 

 any claim whatever to be received as even 

 a possible hypothesis ; all the facts on which 

 it claimed to rest having either been them- 

 selves disproved, or having been found satis- 

 factory explicable on the general principle 

 omne vivum ex ovo. Thus, the appearance 

 of Animalcules in infusions of decaying 

 organic matter, the springing-up of Fungi 

 in spots to which it would not have been 

 supposed that their germs could have been 

 conveyed, the occurrence of Entozoa in the 

 bodies of various animals into which it 

 seemed almost beyond possibility that their 

 eggs could have been introduced, with 

 other facts of a like nature, may now be 

 accounted for, without any violation of 

 probability, by our increased knowledge of 

 the mode in which these organisms are pro- 

 pagated. Thus, it is now well ascertained 

 that the germs of Fungi and of many lands 

 of Animalcules are diffused through the 

 atmosphere, and are conveyed by its move- 

 ments in every direction ; and that, if to de- 

 composing substances of a kind that would 

 otherwise have been most abundantly peo- 

 pled by these organisms, such air only be 

 allowed to have access as has been deprived 

 of its organic germs by filtration (so to 

 speak) through a red-hot tube or strong 

 sulphuric acid, no living organisms will 

 make their appearance in them ; whilst in 

 a few hours after the exposure of the very 

 same substances to ordinary atmospheric 

 air, it has been found to be crowded with 

 life.* And when it is borne in mind, in the 

 case of the Entozoa, that the members of 



* See the experiments of Schuke, in the " Edinb. New 

 Phil. Journal," 1837, p. 165. 



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