4 INTRODUCTORY. 



sidered as attributes of living matter. (See Herbert Spencer, Principles 

 of Bioloyy, vol. i.) 



It is not, however, the mere presence of proteids which is 

 characteristic of living matter. White-of-egg (albumen) con- 

 tains an abundance of a typical proteid and yet is absolutely life- 

 less. Living matter does not simply contain proteids, but has 

 the power to manufacture them out of other substances ; and 

 this is a property of living matter exclusively. 



The powers of living matter are still more characteristic. It 

 is continually wasting away by a kind of internal combustion, 

 but continually repairs the waste by the processes of growth. 

 Moreover, this growth is of a characteristic kind, differing abso- 

 lutely from the so-called growth of lifeless things. Crystals and 

 other lifeless bodies grow, if at all, by accretion, or the addition 

 of new particles to the outside. Living matter grows from within 

 by intus-susception, or taking in new particles, and fitting them 

 into the interstices between those already present, throughout 

 the whole mass. And, lastly, living matter not only thus repairs 

 its own waste, but also gives rise by reproduction to new masses 

 of living matter which become detached from the parent mass 

 and enter forthwith upon an independent existence. 



We may perceive how extraordinary these properties are by 

 supposing a locomotive engine to possess like powers: to carry 

 on a process of self-repair in order to compensate for wear, to grow 

 and increase in size, detaching from itself at intervals pieces of 

 brass or iron endowed with the power of growing up step by step 

 into other locomotives capable of running themselves, and of re- 

 producing new locomotives in their turn. Precisely these things 

 are done by every living thing, and nothing in any degree com- 

 j>;inible with them takes place in the lifeless world. 



llii.xlrv h;'s given the U'M Mutcment extant of the distinctive properties 

 of living matter, as follows: 



"1. Its chemical composition containing, as it invariably does, one or 

 more forms of a complex compound of carbon, hydrogen, oxygen, and ni- 

 trogen, the so-called protein (which has never yet been obtained except as a 

 product of living bodies), united \vith a large proportion of water, and 

 forming the chief constituent of a .substance which, in its primary unmod- 

 ified state, is known as protoplasm. 



"2. Its universal disintegration and waste by oxidation, <in<l its con- 

 cuinitant n intt ///<<? inn /.// ///< ///f>/.s.st/M-> jjti<m of new matter. A. process of 



