1895.] Zoology. 503 



sight in both monkeys and dogs. The experience of the author, con- 

 cerning this point agrees with that of M. H. Munck and confirms 

 his conclusions. The later researches of different scientists have con- 

 firmed the facts which he demonstrated. 



Kepeating the experiment of total extirpation of the two occipital 

 lobes of monkey, February 19, 1893, M. Vitzou noticed that during the 

 fourth month the animal commenced to perceive persons and objects, 

 but with great difficulty. At the end of fourteen months, the ability 

 to perceive was greatly increased. The monkey could avoid obstacles, 

 which he could not do during the first months following the operation. 



On the 24th, of April, 1895, Mr. Vitzou repeated the operation 

 upon the same animal. After denuding the skull he found the orifices 

 of trepanation closed by a mass of rather firm connective tissue. On 

 lifting this mass with care, to his astonishment and that of the assistants 

 standing about him, he found the entire space which had formerly 

 been occupied by the occipital lobes completely filled with a mass of 

 new formed substance. This he proceeded at once to examine. 



A portion was taken from the centre of the mass closing the orifice 

 of trepanation, and another from the posterior part of the new formed 

 substance found in the skull. Employing both the rapid method of 

 Golgi and Eamon y Cajal, and the method of double coloration with 

 hematoxyline of Erlich and eosine in aquous solution, M. Vitzou 

 demonstrated the presence of pyramidal nervous cells and of nerve 

 fibres. The nerve tissue was present in large quantities and the nerve 

 cells less numerous than in the occipital lobes of the adult animal, but 

 their presence in the new formed mass was constant. 



In brief the conclusion from the preceding experiment is that the 

 new substance occupying the place of the occipital lobes, was of 

 nerve nature, and that it was due to a new formation of cells and of 

 nerve fibres in the brain of the monkey. Here is a fact, says the 

 author, which demonstrates the possibility of regeneration of nerve 

 tissues in the brain, as well as, what was previously known, that active 

 nutrition is maintained in the rest of the organ. 



Moreover, we find in the presence of cells and nerve fibres in the 

 new formed mass an explanation of the fact concerning the betterment, 

 although slight, of the 'sense of sight. This explains also contradic- 

 tory facts presented by different scientists, in the case of partial extir- 

 pation of the brain followed -by an amelioration of the functions lost 

 during the first operation. 



M. Vitzou adds that the monkey having been subjected to a second 

 operation lost the sight from both eyes for three months and a half, at 



