CH. xxiv. BONNET AND SPALLANZANL 201 



treated in this way. Bonnet, however, and the famous 

 Italian naturalist Spallanzani (1729-1799) proved by a great! 

 number of experiments that tails, legs, and even heads will 

 grow again in some animals, after they have been cut off. 

 The garden-worm, for example, is an animal with many 

 organs : it has numerous bristles, which serve as feet, it has 

 arteries and veins, nerves, and organs of digestion, and a 

 mouth ; yet Bonnet found that a worm if cut in pieces would 

 grow a new head or a new tail, and, what was still more 

 curious, in some rare cases it grew the head on the end where 

 the tail had been before ! Spallanzani went even farther, 

 for he experimented on snails. Now the common garden 

 snail has a head with four horns, moved by very complicated 

 muscles, and two of these horns have eyes at the end oi 

 them ; moreover it has a mouth, with a horny jaw and a 

 tongue armed with innumerable small teeth. Spallanzani 

 cut off first the horns with eyes, and afterwards the mouth 

 and tongue, and found that the snail had power to re-grow 

 them all. He then tried upon aquatic salamanders, which 

 resemble our newts, or efts. These creatures have red blood 

 like ourselves, they have a heart, lungs, bones, and muscles, 

 and their legs possess muscles and nerves like those of a 

 man ; yet Spallanzani cut off the tail and legs of one sala- 

 mander six times in succession, and in another case, Bonnet 

 cut them off eight times, and they grew again. Bonnet even 

 took out the right eye of a newt, or eft, and in eight months 

 another eye had grown in its place. These experiments werej 

 very startling, for they showed that the life of the lower 

 animals does not so much depend on a particular part of I 

 the body, as it does in ourselves and in the higher animals. \ 

 If you cut off the head of a man or an ox, they die, or if you 

 cut off a leg, it never grows again ; but these experiments 

 proved that the worm and the snail live and grow new 



