40 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



whose brain I had removed, that light caused the 

 pupil to contract several hours after death, when 

 signs of decomposition had already begun to appear. 

 Steinach has proved that in this case the muscle- 

 elements in the iris are stimulated directly by the light 

 (3). This reflex is therefore determined by the mus- 

 cles of the iris, and the nervous connections serve 

 only as quicker and more sensitive conductors. Thus 

 we see that the eyeball behaves toward light just as 

 the Ascidian behaves toward mechanical stimuli. 



Some physiologists seem to doubt that the muscles 

 can be stimulated directly by light without the inter- 

 vention of the ganglion-cells. But we know that 

 phenomena of contraction are also produced by the 

 light in the unicellular swarmspores of algae, which 

 certainly contain no ganglia. Furthermore, no one 

 doubts that muscles without ganglion-cells can also be 

 stimulated chemically or mechanically. Why should 

 there not also be muscle-fibres that can be stimulated 

 directly by light ? There is no reason for assuming 

 that all muscles must behave exactly like the muscles 

 of the frog's leg, simply because the experiments on 

 it have by chance furnished the prevailing views con- 

 cerning muscles. 



The reader may believe that the pupillary reflex is 

 an exceptional case, but this is not true. Defsecation 

 and urination in higher animals may be considered as 

 reflex phenomena of the spinal cord. The pressure of 

 the faeces or of the urine acts as a stimulus, which 

 affects the centres for the activity of the muscles of 



