22 THE BEGINNINGS OF LIFE. 



particles of protoplasm is, within certain limits, di- 

 rectly dependent upon temperature. By variations of 

 this, the rapidity of movement of the particles in 

 the cell may be seen to be increased or diminished 

 at pleasure. The amoeboid activity of a white blood 

 corpuscle or of a pus corpuscle is similarly stimu- 

 lated, within certain limits, by the influence of heat. 

 We know also that the hatching of eggs and the 

 germination of seeds may be likewise hastened or 

 retarded by access or deprivation of heat. Considera- 

 tions such as these at first suggested the doctrine of 

 the Correlation of the Vital and the Physical Forces, 

 a doctrine which has been slowly, though surely, gain- 

 ing ground since the date of its first announcement. 

 More and more evidence is gradually being accumu- 

 lated in its favour, so that we now find Professor 

 Frankland alluding to it in these terms: c No one 

 possessing any knowledge of physical science would 

 now venture to hold that vital force 1 is the source 

 of muscular power. An animal, however high its or- 

 ganization, can no more generate an amount of force 

 capable of moving a grain of sand, than a stone can 

 fall upwards, or a locomotive drive a train without fuel.' 

 Mr. Herbert Spencer, also, speaking of the same doc- 

 trine, says 2 , c It is a corollary from that primordial truth 

 which, as we have seen, underlies all other truths, that 



1 That is, any peculiar force existing of and I>y itself, independently of 

 nil the physical forces. See Proceed, of Royal Institution, June 8, 1866. 

 8 ' Principles of Biology,' vol. i. p. 57. 



