452 PROCEEDINGS OF THE AMERICAN ACADEMY. 



a cell body, aud by passing from one neuron to another. Wundt found 

 that the delay in the spinal ganglion cell of man was 0.003 second. 

 The delay in passing between different neurons is probably greater, say 

 0.005. So in man, if two cell bodies and two contacts between separ- 

 ate neurons are to be traversed, the loss of time would be ([0.003 X 2] -[- 

 [0.005 X 2] =) 0.016 second. In lower animals, as is well known, the 

 time reactions are much greater. It is quite probable that in some of the 

 lower animals this short circuit may mean the saving of a considerable 

 fraction of a second. 



An animal suddenly confronted with some optical evidence of danger 

 from which it recoils in fear, does so reflexly, calling into operation this 

 apparatus. When we pause to consider how often in the struggle for 

 existence the saving of a fraction of a second may be a question between 

 life and death, we see how important a part this apparatus may have 

 played throughout the vertebrate series in the survival of the fittest. 



