1 2 PROTOZOA 



The death of the living being finds a certain analogy in the 

 breaking up or the wearing out of a piece of machinery ; but in 

 no piece of machinery do we find the varied irritabilities, all 

 conducive to the well-being of the organism (under ordinary 

 conditions), or the so-called " automatic processes " ^ that enable 

 the living being to go through its characteristic functions, to 

 grow, and as we shall see, even to turn conditions unfavourable 

 for active life and growth to the ultimate weal of the species 

 (see p. 32). At the same time, we fully recognise that for 

 supplies of matter and energy the organism, like the machine, 

 depends absolutely on sources from without. The debtor and 

 creditor sheet, in respect of matter and energy, can be proved to 

 balance between the outside world and Higher Organisms with 

 the utmost accuracy that our instruments can attain ; and we 

 infer that this holds for the Lower Organisms also. Many of 

 the changes within the organism can be expressed in terms of 

 chemistry and physics ; but it is far more impossiljle to state 

 them all in such terms than it would Ije to describe a 

 polyphase electrical installation in terms of dynamics and 

 hydraulics. And so far at least we are justified in speaking of 

 " vital forces." 



The living substance of protoplasm contains a large quantity 

 of water, at least two-thirds its mass, as we have seen, in a state 

 of physical or loose chemical combination with solids : these on 

 death yield proteids and nucleo-proteids." The living protoplasm 



' ' mucilage "] or of a jelly. Now the phenomena of protoplasmic motions as studied 

 in the Rhizopoda and in the vegetable cell, seem absolutely to preclude the jelly 

 Hn[)position, and for these cases we must admit that living protoplasm is a viscid 

 li(iuid whose refractivity is probably the mean of the two constituents separated 

 by death, the one solid, the other a watery solution : and death is for us essentially 

 a process of precipation (or better, " desolution "). For further work on these 

 lines see Hardy in Journ. Physiol, vol. xxiv. 1899, p. 158, and Fischer, Fixlrumj u. 

 Fdrbung, 1900. 



' In its original use "automatism" designates the continuous sequence and 

 combination of actions, without external interference, ])erformed by complex machines 

 designed and made for specific ends by intelligent beings : thus we speak correctly 

 of "automatic ball bearings " that tighten of themselves when they become loose ; 

 but even these cannot take up fresh steel and redeposit it, either to replace the 

 worn parts or to strengthen a tube that is bending under a stress. 



- Proteids are organic compounds containing carbon, hydrogen, nitrogen, and 

 oxygen, of which white of egg (albumen) is a familiar type. Nucleo-proteids are 

 compounds of jiroteids with nucleinic acid, which in addition to the above elements 

 contain phosphorus. 



