CENTRIFUGAL MOVEMENTS. 8'l 



There can be no doubt that the smallest particle of 

 living matter is complex. It is impossible to conceive 

 the existence of a living particle of any simple substance 

 like iron, oxygen, nitrogen, &c. ; for living involves changes 

 in which several different elements take part. It seems 

 to me, therefore, that the term living atom cannot with 

 propriety be employed, seeing that living matter is of 

 complex composition, while the idea of an atom seems to 

 involve simplicity of constitution, if not indivisibility. The 

 whole question of the arrangement and form of the atoms 

 in living matter can at present only be discussed theoreti- 

 cally ; and I would now merely remark with reference to 

 this subject, that although all living particles are of complex 

 composition, many different elements may exist in very 

 different proportions in living matter; and that there is 

 reason to believe that the smallest particles of every kind of 

 living matter are spherical. It is not possible to see, with 

 the highest powers now made, particles which would in all 

 probability be demonstrable by more perfect glasses. But 

 there is reason to think that in any case we must fail to see 

 the actual particles, which are the seat of change, in con- 

 sequence of their extreme tenuity and transparency. The 

 further consideration of this question is of the deepest 

 interest; but from this point the inquiry assumes a too 

 purely speculative character for me to pursue it here, as I 

 am anxious not to diverge very far from the consideration 

 of phenomena which can be investigated by observation 

 and experiment. It seems however to me probable 

 that the wonderful changes occurring when inanimate 

 matter becomes living, which occur in living beings alone, 



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