228 

 amounts came into play in cause and effect, we raiiet consider 

 ^K?f .?=^f^^^!.^-''\!F"°*^' ^" ^"^^i«^ *^^r^ ^« a. Very notice- 

 fSi^Jn^nf^^^^''^^^^'!^^ the ariount of energy f fen ifehed by 

 the stiraulati(^n'and that expended in the effect," on the part 



lLll^^ ^VynfiLlHl'^^'iM JS"^ '''^"'^"* °^ ^^^^^Y expended by 

 Jn^.^i^l/tJ^f^^t »".^^^'^ tJt-oueht to,it^ I7e will term an 

 e'ffect df the^kind fii-et ttt^med/ the !8orce,,>^f'ffe<;t . one of the 



?^°?*^J. ^i^^tS". ^^^Tl'V^^^''^' Th e 'ener gy Su pp lied tyan ef- 

 -feet the oj:'|anlsm m both v/ays. Wfeile the f«i-ce effect is in- 

 dependent ^>f the ehfe^rgetic condition of the <>ell, no stimulus 

 effect can be prod^ts^d.. without a sufficient and available amount 

 of potential energy, whli;h> in the process of stlmilation, can 



^S^*^^'^?^^!*®^ ^y *^® °®11 ^^^^ ^otwal energy^ Each stimulus 

 effect IS therefore dependent first of dil On the energetic 

 condition of the cell and may in this sense be ctinsidered as 

 having been accomplished by the cell itself. 



Although the above-said makes clear the ^jrincipiii difference 

 between the force effect and the stimulus effect it v.ill not 

 always be possible, when judging of single processed, to decide 

 which class of effect is concerned in each. If ^ for example, a 

 cell divides, under the influence of any fiactors whatever, v/e 

 will not be able to say whether the amount of energjr fiirnished 

 Is equal to that exj^ended in the proceftR named pr n^t. Such 

 difficulties confront us also when judging of almost all the re- 

 maining processes of groTrth and formation. Since in this treat- 

 (860) ise these processes of growth and formation are concerned, it 

 will therefore be advisable in the use of the word. -"stimulus 

 effect" to mal?e ourselves independent of any considerations re- 

 garding energy and its use and, Y/ith Herbst-'-, to speak of stim- 

 ulus effect in all those cases in which any cm ee t/hatever *'may 

 induce a resulting phenomenon in some living organism", - "be- 

 cause of the unexpected character which these resulting phenom- 

 ena always have". Accordingly, we will venture to speak of 

 force effects only when we can understand in terras of energy 

 the ones observed on the organism or when they tttake possible 

 conclusions as to the proportionate amounts of energy and in so 

 far have no longer any "unexpected quality". iStimulus effect 

 takes place in almost every ease with which we shall be occupied: 

 all processes of growth and differentiation are the reaction of 

 the living organisms to some stimulus* ^ ♦ 



Various tjtpes of stimulus effect may be ftietinguished, ac- 

 cording to the nature of the stimulating ageni as well as *« 

 the character of the reqctlon to the stimtilti^i. 



Every occurrence in animate as in inaniltette nature involves 

 some change, Me can, however, think of changes cf -all kinds 

 only as being brought about as the result ana effe-ot -of isome 

 other change. Also, each procesB of formation and differentiation 

 may not be imagined otherwise than as the e^f^ct of some change 

 in one of the many factors influencihg the cell life, 



■^ Ueber die Bedeutung d, Reizphysiologie etc. S, Tl. Biolog, 



cbi,, leas, Bd. XV, p* tsi, 



^ It is possible that with a better knowledge of cell 

 physiology and the mechanics of the protoplasm, many a "stimulus 

 effect" will lose its, to us, "unexpected" character and will be 

 shown possibly as a force effect. We are at present very tar 

 indeed from having this insight into cell life. 



