356 GENERAL PHYSIOLOGY 



different phenomena. This great multiplicity in the phenomena 

 of stimulation, in combination with the fact that general reactions 

 have not yet been investigated systematically, make it at present 

 very difficult to deduce from the facts general laws for reactions. 

 Nevertheless, it is possible to establish empirically for groups of 

 stimulation-phenomena common peculiarities. 



The changes that spontaneous vital phenomena experience under 

 the influence of stimuli are of various kinds. In the first place, the 

 phenomena may continue unchanged in quality and undergo 

 quantitative changes only. This may be expressed either in an 

 augmentation of all, or of single phenomena the reaction is 

 then termed excitation [Erregung] or in a diminution of all 

 or single phenomena the reaction is then termed depression 

 [Ldhmung]. 1 



In the second place, spontaneous vital phenomena may be wholly 

 changed in kind, so that wholly new phenomena appear which 

 otherwise do not occur at all in the life of the cell. Such reactions 

 occur, e.g., in the metamorphic phenomena of necrobiotic processes, 2 

 where under many influences not yet wholly known the cells of the 

 body form substances, such as amyloid substance, which are 

 completely foreign to them in normal life. These reactions have 

 been very little investigated, and, so far as one can now judge, it 

 appears as if they are only secondary results of quantitative changes 

 of normal vital phenomena. Thus, it can be imagined that in 

 metamorphic processes the appearance of foreign substances in the 

 cell depends upon the fact that, as a result of chronic stimulation, one 

 or more processes in the normal metabolism are gradually decreased 

 or have entirely dropped out, so that compounds that normally are 

 formed, but on account of immediate further transformation do not 

 accumulate, are now stored in quantity, because the processes in 

 the metabolism that are necessary to their transformation no longer 

 exist. For the present, however, this must remain an hypothesis. 

 The following consideration will have to do chiefly with the pheno- 

 mena of excitation and depression. It is not superfluous sharply 

 to emphasize our conceptions of stimulus, excitation, and depression, 

 as well as the relations of these to one another, since not 

 rarely in physiology because of the false idea, usually assumed, 

 that a stimulus must always produce excitation, much confusion 

 and difficulty in the judgment of phenomena have arisen. 

 These can be avoided if the following definitions be accepted : 



1 [The best English equivalent of the word Erregung seems to me to be 

 "excitation." The translation of the word Lahmung has given some trouble. 

 The customary English equivalent of the word is " paralysis," but it is easy to 

 see that such a rendering would not convey the exact meaning of the author. 

 After considering and rejecting various proposed terms, I have finally decided to 

 adopt as the opposite of excitation the comparatively unobjectionable word 

 < ' depression." F. S. L.] 



2 Cf. p. 330. 



