4 LIVING PARTIOLES. 



rescue pbysiology, for a time at least, from being con- 

 sidered a mere subsection of physics. 



6. Living particles. — It is difficult for the mind to 

 realise the wondei^ful minuteness, the extraordinary 

 number, and the almost universal distribution of par- 

 ticles of living matter. Not only are they found in 

 'ind upon the earth and water, but the air teems with 

 them, and is, as is well known, the medium by which 

 some particles of comparatively large size and even of 

 complex organisation are carried from the place of 

 their formation to the seat of their development and 

 growth. But of microscopic germs the air contains 

 vast quantities differing entirely in their nature, their 

 mode of origin, and in the results of their develop- 

 ment. Living particles giving rise to various forms 

 of microscopic fungi are wafted by currents of air 

 into situations favourable for their development, and 

 may become the active agents in every kind of fer- 

 mentation and putrefaction, as has been proved by 

 Pasteur. In the same way there is reason to think 

 particles of living matter capable of giving rise to the 

 most serious and fatal diseases of which man is the 

 subject are carried to an organism which is in a state 

 favourable for their reception and germination. No 

 doubt millions of such living particles perish for every 

 one that germinates. Some are much more easily 

 destroyed than others. Certain kinds retain their 

 vitality for a comparatively long time in a moist warm 

 atmosphere, and it is not improbable that they may 

 even grow and multiply, and perhaps produce particles 

 differing from them in properties or powers. Some 

 of these particles possess inherent motion, and it is 

 probable that they climb, as it were, through still and 

 moist air, just as amoebge and certain other living par- 

 ticles are capable of climbing in any direction through 

 water which is in a state of perfect rest. Minute par- 

 ticles possessing these inherent powers of active move- 

 ment can insinuate themselves into the slight chinks 



