INSENSIBILITY OF THE LOWER ANIMALS TO PAIN. 161 



to inJTiry ; while, on the other hand, as we descend 

 in the scale of being, we find that the nervous 

 system is more and more imperfectly organised : 

 until at last, on arriving among the insects and 

 annelids, to which latter class the earth-worm be- 

 longs, we lose all vestige of a brain, and find its place 

 only imperfectly supplied by a system of little knots of 

 nervous tissue, arranged in pairs along the interior 

 inferior part of the body, called ganglions. It is this 

 imperfect development of the nervous system, and 

 comparative insensibility to pain or physical injury, 

 that enables them to endure, with seeming impunity 

 and indifference, mutilations which would produce in- 

 stant death to any member of the higher orders. For 

 instance, a worm will continue alive for upwards of 

 an hour, though impaled from head to tail upon 

 a hook. How long would a human being live in 

 such a predicament ? Again, if it is cut through the 

 middle, the upper part of the body will not perish, but 

 will speedily reproduce the part that is lost, and re-form 

 a perfect animal. I have witnessed this reproductive 

 process going on in the worm on numerous occasions. 

 Pull a limb off a spider. He cares very Ijttle about it, 

 and will scuttle off with the remainder as nimbly as if 

 nothing had happened ; and a new limb will shortly 

 replace the lost member. And when we direct our 

 attention to reptiles and fishes, a higher class of beings, 

 we will find even them endowed with a wonderful 

 degree of immunity from physical injury, as proved by 



the following anecdotes. 



H 2 



