MENTAL AND SOCIAL EVOLUTION 121 



normal position. But it cannot pick up food for itself, 

 it cannot avoid danger, indeed it does not recognize 

 danger, it cannot fly. These powers depend on the 

 co-ordinate action of its higher brain cells, and the 

 removal of these cells reduces its activities to the condi- 

 tion of a lower order, from which it sprang. No one 

 has been able to carry on similar experiments with the 

 higher mammals, because of the resulting shock, and 

 the uncontrolable hemorrhage ; and of course experiments 

 on human beings are out of the question. But, there 

 is good reason to believe, that if these normal and tech- 

 nical difficulties could be eliminated, the trained physiolo- 

 gist could carry a man back, by the successive steps of 

 his evolution, from lower orders, first, in the scale of 

 civilization, and then in that of organic life, by simply 

 destroying, in succession, the physical centers of the 

 brain, from the highest to the lowest. There are many 

 eases, in medical literature, of insanity resulting from 

 injury to the brain, and disappearing when the injury 

 was cured. In some of these cases the injured person, 

 while retaining nearly complete control of his mental 

 faculties, lost all sense of moral accountability, and com- 

 mitted grave offenses. Certain diseases, especially par- 

 etic dementia, produce the same effect, and these diseases 

 have for their constant lesions, the destruction of the 

 brain tissue. 



The phenomena of anaesthesia furnish similar evi- 

 dence. Physically the person going under chloroform, or 

 ether, loses first conscious sensibility, then unconscious 

 sensibility in the voluntary muscles, then the peristaltic 

 action of the involuntary muscles of the coats of the 

 intestines stops, and finally, if the anaesthetic is pushed, 

 the heart ceases to beat. Mentally, the same order is 

 followed, the reverse order of development. The pa- 



