62 



THE AMERICAN MONTHLY 



[April, 



and design on the part of plant and 

 animal, they do not necessarily imply 

 any psychic process, and there is no 

 evidence to show that the organisms 

 exhibiting them are aware of the de- 

 sign ; in other words, there is no con- 

 sciousness, in a psychic sense. The 

 lowest or most restricted form of 

 sensation is, however, inseparable 

 from knowledge in its essence, which 

 implies discrimination of difference 

 or agreement. Engelmann describes 

 how the fluent jelly of the so-called 

 ' flowers of tan ' {.^thalium septi- 

 cuni)^ while. creeping about upon the 

 spent tan bark, w^ill draw itself into 

 the deeper parts upon being suddenly 

 exposed to the irritation of bright 

 light ; likewise, how the great fresh- 

 water amoeba-like organism Pelo- 

 7)iyxa palustris creeps about quite 

 vigorously in the dark, but upon be- 

 ing suddenly illuminated it will with- 

 in a few seconds assume a spherical 

 shape, the granular streaming having 

 previously ceased. Every student of 

 plant histolog}^ knows how extremely 

 sensitive to mechanical irritation of 

 any kind are the protoplasmic threads 

 and currents of plant-cells ; the fresh- 

 ly-made preparations showing only 

 motionless protoplasm, which re- 

 sumes its activity after the prepara- 

 tion has had a period of rest. 



The selenotropic and heliotropic 

 movements of plants, as well as the 

 so-called 'movements of irritability' 

 in plants recognized as ' sensitive,' 

 and also in those not generally sup- 

 posed to possess this property, all go 

 to make up a mass of evidence to 

 prove the existence of a fundamental 

 sensitivit}' both phototropic and me- 

 chanical in all living organic matter. 

 America's most eminent microscopist 

 has pointed out how that mere jelly- 

 speck, the rhizopod, moves about 

 with the apparent purposes of more 

 complex creatures ; evidentl}^ possess- 

 ing a power of discrimination and se- 

 lection of its food, since it commonly 

 rejects dead diatom shells and the 

 empty cells of other algse. Dar-win, 

 on the other hand, has shown how 



the sundew^ will always seize upon 

 substances of an organic nature, while 

 inorganic matter, such as glass, chalk, 

 stone, or metallic substances, will be 

 rejected, the highly sensitive glandu- 

 lar hairs making little or no move- 

 ment towards the particles placed 

 upon the leaf, and, notwithstanding 

 the highly nervous temperament of 

 the leaves, cutting or pinching them 

 causes no movement, and gusts of 

 wind or drops of rain are without 

 effect. The microscopist, therefore, 

 whether using his instrument or not, 

 has presented to him an unconscious, 

 organic discrimination of impi'essions, 

 followed by purposive movements, 

 which must lead him to conclude that 

 all animal and most plant actions are 

 the result of sensibility. 



Motion is an essential condition of 

 life, and Aristotle traced all motion 

 to impulses rising, in the nature of 

 things, from the common sensibilities 

 of life. Motility and sensibility are cor- 

 relative properties, inseparable from 

 one another. We speak improperly 

 of the ' spontaneous movements ' of 

 protoplasm. There is no spontaniety 

 in life, either in its genesis or its func- 

 tions. Movement is determined by 

 the influence of an agent ; this agent 

 is the excitant. The property of re- 

 action after excitation, as indicated by 

 mechanical, neural, or psychic mani- 

 festations, is irritability. Some have 

 regarded irritability as an elementary 

 form of sensibility, sensibility an ex- ' 

 alted expi'ession of irritability. Chem- 

 istry throws no light upon the func- 

 tions or development of nervous mat- 

 ter, and the microscope shows us that 

 the matter immediately concerned in 

 nervous manifestations is, in the high- 

 est forms, composed of the same col- 

 orless, moving substance which con- 

 stitutes the living matter of the lowest 

 organisms. The protoplasm of the 

 lower forms of life and the ganglionic 

 tissue of higher forms are similar. 

 Sensibility is a property inherent in 

 both. Nerves are but specialized 

 pseudopodia adapted to conveying 

 excitation from one ganglion to an- 



