282 ZOOLOGICAL PHILOSOPHY 



sively extinct in the principal organs in a regular and constant order ; 

 and the moment at which Ufe ceases in the last organ is that which 

 completes the death of the individual. 



On such difficult subjects as those of which I have been treating, 

 we are closely confined within the limits of knowledge and to the 

 sphere of what we can learn from observation. Everything has 

 reference to the conditions essential to life in a body ; conditions 

 established in compliance with facts which prove their necessity. 



If things are not really as I have described, or if it is held that the 

 conditions named and the admitted facts which testify to the true 

 foundation of these matters, are not adequate proofs to justify us in 

 admitting them, we shall then have to abandon altogether the enquiry 

 into the physical causes which give rise to the phenomena of life and 

 organisation. 



