36 THE PJEttNCIPLE OP CHAP. I. numerous muscles. Eespiration is partly voluntary, bub mainly reflex., and is performed in the most natural and best manner without the interference of the will. A vast number of complex movements are reflex. As good an instance as can be given is the often-quoted one of a decapitated frog, which cannot of course feel., and cannot consciously perform, any movement. Yet if a drop of acid be placed on the lower surface of the thigh of a frog in this state, it will rub off the drop with the upper surface of the foot of the same leg. If this foot be cut off, it cannot thus act. " After some fruitless efforts., therefore, it gives up trying in that way, seems restless, as though, says Pfliiger, it was seeking some other way, and at last it makes use of the foot of the other leg and succeeds in rubbing off the acid. Notably we have here not merely contractions of muscles, but combined and harmonized contractions in due sequence for a special purpose. These are actions that have all the appear- ance of being guided by intelligence and instigated by will in an animal, the recognized organ of whose intelli- gence and will has been removed." 10 We see the difference between reflex and voluntary movements in very young children not being able to perform, as I arn informed by Sir Henry Holland, cer- tain acts somewhat analogous to those of sneezing and coughing, namely, in their not being able to blow their noses (i. e. to compress the nose and blow violently through the passage), and in their not being able to clear their throats of phlegm. They have to learn to perform these acts, yet they are performed by us, when a little older, almost as easily as reflex actions. Sneezing and coughing, however, can be controlled by the will only partially or not at all; whilst the clearing the throat 10 Dr. Maudsley, « Body and Mind,' 1870, p. 8.