502 PHYSIOLOGY CHAP. 



In this connection the experiments of Magendie (1825), Bouillaud 

 (1850), Longet (1847), Keuzi (1863), and Lussana and Lemoigne 

 (1871) are highly important. It was the observations of these 

 authors as a whole that laid the foundation of the generally 

 accepted psychological distinction between crude sensations or 

 simple psychical impressions on the central sense-organs, and per- 

 ceptions or sensations elaborated by the intellectual centres and 

 referred to the external world. The former are also termed 

 unconscious or passive sensations, the latter conscious or active 

 sensations. Only the last are dependent on the cerebral hemi- 

 spheres, while the first depend on the thalamencephalon, mid- 

 brain, the pons, medulla oblongata, and cord. 



To explain the discrepancy between the results of Flourens 

 and those of Magendie, Longet and Eenzi, it is not enough to 

 insist on the inhibitory effects of traumatism, since we know that 

 Flourens unlike Eolando succeeded in keeping decerebrated 

 pigeons alive for a long time and in observing them for months. 

 Clearly he must have excised the whole or greater part of the 

 optic thalami which represent the 'tween-brain, along with the 

 hemispheres. Longet was the first who attached great importance 

 to the exact delimitation of the cerebral lesions, and he obtained 

 animals deprived of their hemispheres only, without injury to the 

 optic thalami. 



H. Munk (1883) resumed the experiments on pigeons, with 

 the object of deciding the old controversy between Flourens, who 

 concluded that the pigeon deprived of its cerebral lobes " a perdu 

 tous ses sens," and his successors, who held with Cuvier "que 

 les lobes cer^braux sont le receptacle ou toutes les sensations 

 preunent une forme distincte, et laissent des souvenirs durables." 



As we shall presently see, H. Munk in his experiments on 

 dogs and monkeys came to the conclusion that the destruction of 

 certain segments of the cerebral cortex produced total blindness 

 in these animals. If what happens in dogs can also be observed 

 on birds, Munk thought it certain that complete extirpation 

 of both hamispheres must produce results similar to those so 

 excellently described by Flourens, who alcne had made observa- 

 tions on completely decerebrated birds. The error would then, 

 according to Munk, lie, not with Flourens, but with his successors, 

 by whom the cerebral hemispheres of the pigeons were only 

 destroyed incompletely. This operation is more difficult than 

 any other to carry out accurately on account of the uncontrollable 

 haemorrhage. 



Eighty per cent of Munk's pigeons perished. Of the twenty- 

 five that survived, four only were found at the post-mortem to 

 have been completely operated on. These had been subjected to 

 repeated experiments for months after the operation. They were 

 totally blind, and behaved exactly as Flourens described. If 



