26 THE HUMAN BODY. 



proach to it is probably exhibited by the resting state into 

 which some of the lower animals, as the wheel-animalcules, 

 pass when dried slowly at a low temperature; the drying act- 

 ing by checking the nutritive processes, which would other- 

 wise have prevented the reattainment of molecular equilib- 

 rium. All signs of movement or other change disappear 

 under these circumstances, but as soon as water again soaks 

 into their substance and disturbs the existing condition, then 

 the so-called "spontaneous" movements recommence. If, 

 therefore, we use the term spontaneity to express a power in 

 a resting system of particles of initiating changes in itself, it 

 is possessed neither by living nor not-living things. But if 

 we simply employ it to designate changes whose primary 

 cause we do not recognize, and whose cause was in many 

 cases long antecedent to the changes which we see, then the 

 term is unobjectionable and convenient, as it serves to ex- 

 press briefly a phenomenon presented by many living things 

 and finding its highest manifestation in many human actions. 

 It then, however, no longer designates a property peculiar to 

 them. A steam-engine with its furnace lighted and water in 

 its boiler may be set in motion by opening a valve, and the 

 movements thus started will continue spontaneously, in the 

 above sense, until the coals or water are used up. The differ- 

 ence between it and the living cell lies not in any spontaneity 

 of the latter, but in its nutritive powers, which enable it to 

 replace continually what answers to the coals and water of 

 the engine. 



Protoplasm. The cell-body was formerly regarded as es- 

 sentially made up of a single substance, which was named 

 protoplasm : and now that its structure is known to be com- 

 plex the term is retained as a convenient one for that mixture 

 of spongioplasm and hyaloplasm which constitutes the main 

 bulk of the bodies of most cells. With the protoplasm other . 

 things are frequently presen^the most important ofjyjikili 

 are either materials undergoing anabolic changes butno-t ^vet 

 completely built up into protoplasm, or katabolic materials 

 rpsnmnfr from the chemical degradation of protoplasm": 

 these secondary matters, mingled with the completed proto- 

 plasm, are conveniently spoken of as the cell deutoplasm or 

 par a plasm. As between the spongioplasm and hyaloplasm 

 there are still some differences of opinion as to which is the 

 more immediate agent in the manifestation of the vital activ- 



