ELKMKNTAKY I'KOBLEMS IN I'll YSIOLOGV. 431 



To complete this outline, so far as I can to-day, I have but one other 

 consideration to bring before you, one which is connected with the last 

 of my four points of departure, — that of the relation of oxygen to proto- 

 plasm, a relation which springs out of the avidity with which, without 

 being oxidized or even sensibly altered in chemical constitution, it seizes 

 upon oxygen and stores it for its own purposes. The consideration 

 wlii(;h this suggests is tliat if the oxygen and oxidi/able material are 

 constantly stored, they must either constantly or at intervals be dis- 

 charged ; and inasmuch as we know that in every instance, without 

 exception, in which heat is produced or work is done, these processes 

 have discharge of water and of carbon dioxide for their concomitants, 

 we are justified in regarding these discharges as th« sign of expenditure, 

 the charging with oxygen as the sign of restitution.- In other words, a 

 new characteristic oT living process springs out of those we have already 

 had before us, namely, that it is a constantly recurring alternation of 

 opposite and complementary states, that of activity or discharge, that 

 of rest or restitution. 



Is it so or is it not ? In the minds of most i)hysiologists the distinction 

 between the phenomena of discharge and the phenomena of restitution 

 ( Krbolung) is fundamental, but beyond this, unanimity ceases. One dis- 

 tinguished man in Germany and one in England — Professor Heringand 

 Dr. Gaskell — have taken, on independent grounds, a different view to 

 tlie one suggested, according to which life consists not of alternations 

 between rest aiul activity, charge and discharge, loading and exploding, 

 but between two kinds of activity, two kinds of explosion, which differ 

 only in the direction in which they act, in the circumstance that they 

 are antagonistic to each other. 



Xow when we compare the two processes of rest, which as regards 

 living matter means restitution, and discharge which means action, 

 with each, other, they may further be distinguished in this respect, that 

 whereas restitution is autonomic, /. e., goes on continuously like tlie ad- 

 ministrative functions of a well-ordered community, the other is occa- 

 sional, i. e., takes place only at the suggestion of external intluences; 

 that, in other words, the contrast between action and rest is (in i elation 

 to protoplasm) essentially the same as between waking and sleeping. 



It is in accordance with this analogy between the alternation of wak- 

 ing and sleeping of the wliole organism, and the corresponding alterna. 

 tion of restitution and discharge, of every kind of living substance, that 

 l)hysiologists by common consent use the term stimulus {Rciz, Pr!l-1ccJin(/)y 

 meaning tiiereby nothing more than that it is by external disturbing or 

 interfering influence of some kind that energies stored in living material 

 are (for the most part suddenly) discharged. Now, if I were to main- 

 tain that restitution is not autonomic, but determined, as waking is, by 

 an external stimulus, — that it differed from waking only in the direction 

 of whi(;h the stimulation acts, /. e., in the tendency towards construction 

 on the one liand, towards destruction on the other, F sJiould fairly and 

 as clearly as possible express tlie doctrine which, as T have said, the two 



