THE GENERAL EFFECT OF STIMULATION 67 



sea water mixed with ether. The development of the eggs now 

 comes to a standstill. The narcotic has produced an inhibition 

 of development. 



To quote another instance. Bacterium phosphorescens having 

 been bred upon a putrid fish are exposed in the culture fluid to 

 the air. In the dark the bacteria give forth a phosphorescent 

 light. Then the culture fluid containing the bacteria is put into 

 a glass receptacle, which can be rendered air-tight and all oxygen 

 excluded. After a short time the light formation ceases com- 

 pletely. The absence of oxygen has here had a depressing effect 

 and it is only after air has been again introduced that light is once 

 more produced. 



Lastly, an example from the group of mammals may be cited. 

 The metabolism of a dog in complete rest is examined for a pro- 

 longed length of time and we ascertain the values of the oxygen 

 consumption, the carbon dioxide production, and the nitrogen 

 elimination in the urine. Under the same nutritive conditions 

 the animal is then allowed to work from time to time in a tread- 

 mill. During these working periods impulses of excitation are 

 continually conducted to the muscles from the nervous system. 

 It is now found that under the influence of the constantly re- 

 curring stimuli the quantity of nitrogen in the urine has only 

 very slightly augmented, whereas the consumption of oxygen and 

 the production of carbon dioxide has markedly increased. 



What conclusions can be drawn from these instances of re- 

 sponse to stimuli, of which any number could still be quoted? 

 They show us, first of all, that a state or process existing under 

 given conditions, is altered by the influence of the stimulus. This 

 is a fact, however, which could be expected from the beginning 

 and is self-evident, for stimuli are alterations in the vital condi- 

 tions, and when these are altered the state of the system or the 

 happenings thereof must also alter. The question with which 

 we are here more closely concerned, however, is a somewhat 

 more detailed characterization of the state or process itself, as 

 well as that of alterations produced by the influence of the stimu- 

 lus. The instances of response to stimuli already cited furnish 

 us with information in both kinds. 



