1884.] 



MICROSCOPICAL JOURNAL. 



63 



other, and if we study the cells and 

 fibres in the ganglia of the lowest and 

 highest orders we will still encounter 

 the same fundamental constituents of 

 structure. Our conclusion must there- 

 fore be that nervous phenomena are 

 not due, as Sylvius taught, to the 

 chemical composition of, or processes 

 taking place in, the body-substance, 

 nor to thermo-electric currents set up 

 by differences of temperature between 

 the interior and surface of living 

 bodies, as Garrod suggests, but to an 

 unstable molecular balance, or ar- 

 rangement, peculiar to living matter, 

 constituting irritability or sensibility, 

 general at first, specialized later. This 

 theory is one of vital mechanics, in- 

 nervation being a motor process, aris- 

 ing through definite external pro- 

 cesses, the nerve stimuli. Spencer 

 terms the ganglion cell a ' libero-mo- 

 tor element,' and since we recognize 

 nervous phenomena only m living 

 matter, and in all living matter, and 

 as the principle of the conservation of 

 energy has to do only with motor 

 forces, it would seem to sustain Le 

 Conte's theory that vitality is more 

 than a principle, that it is a force cor- 

 related with and derived from the phys- 

 ical and chemical forces, the soul being, 

 like Peter Schlemiehl's, an example 

 of 'polarized activity.' The power 

 of continually adjusting internal with 

 external relations depends upon ex- 

 perience, and experience depends 

 upon memory. We must therefore 

 consider one of the chief factors in 

 the history of nervous development to 

 be that prcemial nervous capacity of 

 living matter for retaining impres- 

 sions of inherent or excited changes 

 spoken of as ' organic memory,' which 

 gives rise to all that class of move- 

 ments called secondary, automatic, 

 or acquired. By means of this or- 

 ganic or unconscious memory, not 

 only the characteristic peculiarities 

 of an organism are carried over from 

 one generation to another, but new 

 experiences acquired through adap- 

 tation to changes of environment are 

 retained. 



Irritability or sensibility is the 

 power of formative material to per- 

 ceive and react to external changes. 

 Organic memory is the faculty which 

 enables form elements to profit by, 

 and adapt themselves to, frequently- 

 recurring changes. Haeckel puts it 

 thus : ' In the very simple and per- 

 sistent forms of life, the plastidules 

 have, so to speak, learned nothing 

 and forgotten nothing. In the highly 

 perfected and variable organisms the 

 plastidules have both learned and for- 

 gotten much.' They have become 

 possessed of what Carpenter has 

 called 'potential knowledge.' From 

 the foregoing it is evident that the 

 protozoans or single-celled animals, 

 as they pass over into the class of 

 metazoans or many-celled, bring with 

 them a heritage of nervous capacity, 

 each morphological element of the 

 compound body contributing a lim- 

 ited power of conducting or storing 

 up nervous energy. Among meta- 

 zoans those dim sensations common 

 in varying degrees to all actively liv- 

 ing matter constituting coena:sthesis^ 

 are transformed into the delicate per- 

 ceptions of the higher animals. The 

 quality of the sensation depends upon 

 the capacity of the specialized tissue 

 for facilitating the flow of nervous in- 

 fluence ; the more elaborate the dif- 

 ferentiation, the higher the grade of 

 consciousness. ' A single individual 

 metazoan being equivalent to a num- 

 ber of protozoa coalesced to form a 

 single organism in a higher state of 

 aggregation,' it becomes necessary 

 that impressions received bv one por- 

 tion of the compound body be im- 

 parted to other portions, and since 

 some parts are more exposed to ex- 

 ternal impressions than others, the 

 nervous disturbance will radiate more 

 frequently along certain lines. Again, 

 some portions of the surface being ex- 

 posed more frequently than others to 

 peculiar forms of irritation, certain 

 lines w'ill gain special facility in trans- 

 mitting these impressions, and as a 

 result the physiologist finds that the 

 Inilk of the vis nervosa is delegated 



