104 SUPER-ORGANIC EVOLUTION 



ated from one another by very clear spaces, pre- 

 sented, moreover, in some places a slight increase 

 in bulk. Senor Tello discovered, then, a fresh 

 appearance of neurofibriles in the vertebrates, and 

 this appearance differs considerably from that till 

 now observed in the mammiferse. 



" Some time after, always in winter, it occurred 

 to Senor Tello to find out what influence might be 

 caused to the nerve-fibres of the lizard on cutting 

 its tail. After the operation the animal, which 

 was then hibernating, awoke suddenly and 

 manifested the greatest excitement. He killed 

 it in this condition, and its marrow was examined, 

 always by the Cajal method. This time the result 

 was still more extraordinary the neurofibriles 

 were numerous and extremely delicate. There was 

 no increase in their volume, and the separating 

 spaces had in great measure disappeared. The 

 appearance offered was almost identical with that 

 of the neurofibriles of a rabbit or some other 

 mammifera (fig. 20). 



" This naturally arrested the attention of Cajal, 

 under whose direction these experiments were 

 being conducted. 'Whence comes this change?' 

 it was asked. ' Why are the neurofibriles of the 

 lizard, when intact, so few and so compact \ Why, 

 when the lizard is mutilated and excited, are they, 

 on the contrary, so numerous and delicate ? ' 



