52 WONDEIJS OF ORGANIC LIFE. 



circulation of the blood in the brain for a 

 moment or two must go on, and then fail, 

 because no supply is afforded. Tortoises have 

 been deprived of their brain, the skin has 

 healed over the vacuum of the skull, and 

 although the senses, such as sight, etc., derived 

 immediately from the brain, were obliterated, 

 the animals have lived and crawled about, 

 dying at length, as it would appear, from inani- 

 tion or cold. 



Besides cerebral and ganglionic life, there is 

 another kind of life, which we may call the life 

 of irritability. We see this life where no nerves 

 exist, and we see it also in muscular fibre 

 deprived of all nervous influence. In the latter 

 case, galvanism excites its display in animals 

 recently killed. It is, however, most con- 

 spicuously exemplified in animals which, 

 deprived of the head and viscera, move about, 

 or in the creeping motion of the muscles of an 

 animal slaughtered and cut up, quivering with 

 unextinguished vitality. Some warm-blooded 

 animals are more remarkable than others for 

 this display of vital irritability. It is, however, 

 in animals destitute of apparent nerves and 

 muscles that its display most surprises us. We 

 may adduce as examples the jelly fishes, 

 {Medusa, Linn.) so common along our shores. 

 These animals move and are sensitive even to 

 the influence of light. The jelly-fish, by a sort 

 of flapping motion, wends its way along the 

 surface of the sea, and by means of pendant 

 tentacles secures its prey ; some species are 



