84 IRRITABILITY 



etc. These, being more difficult to excrete from the cell, accumu- 

 late. These asphyxiation products have in their turn a depressing 

 effect and so on. In this way the whole metabolism is forced into 

 a wrong course. The accumulation of fat in those tissue-cells 

 with an insufficient blood supply, as we have seen in the case of 

 the fat metamorphosis, is doubtless brought about in the same 

 manner by relative oxygen insufficiency. The fatty acids accumu- 

 late as products of an incomplete combustion and combine with 

 glycerine to form neutral fats. In like manner it may be that the 

 accumulation of amyloid substance in amyloid metamorphosis, of 

 lime salts in arteriosclerosis, etc., is produced by a primary 

 depression of the individual constituent processes of the particu- 

 lar cells. 



The relation here described, of the catalytic stimuli to the pro- 

 duction of the metamorphic processes, leads us to the dis- 

 tinctions between primary and secondary effects of stimulation. 

 Should the general fact be established, which has up to now only 

 been pointed out in individual cases, that all the metamorphic 

 processes are merely secondary results of primary alterations in 

 rapidity of individual metabolic constituent processes, then the 

 primary reactions of every stimulus would consist purely in the 

 excitation or depression of the directly -concerned constituent. 

 Whether or not, as may be assumed, this primary effect of stimu- 

 lation applies to all stimuli, is a question which only the future 

 can answer. 



The metamorphic processes are not, however, the only sec- 

 ondary effects of stimulation. The influence of long-continued 

 excitation of the functional constituent processes upon the entire 

 cytoplastic metabolism can be looked upon as a secondary re- 

 sponse. Therefore, they may be considered as a secondary effect 

 of stimulation which, in contrast to this primary excitation, may 

 be called the secondary excitation. 



Further: While the secondary excitation and metamorphic 

 processes are generally produced by the continued existing effects 

 of weak stimulation, we also observe as the result of a stimulus 

 of short duration or frequently repeated at brief intervals, but 

 otherwise not exceeding the physiological limits of intensity, a 



