xhii JouRNAL OF COMPARATIVE NEUROLOGY. 
by the tracts connecting it with the nuclei of the V nerve in the ob- 
longata. The occipital cortex is important for sight. The median 
portion of the dorsal cortex seems to be especially concerned in the 
innervation of the limbs. 
The text of 84 quarto pages is accompanied by eleven text-figures 
and seven plates, five occupied by elegant colored figures representing 
WEIGERT sections and two presenting the results of degeneration ex- 
periments. The paper is one of the most important recent contribu- 
tions to the morphology of the vertebrate brain. 
J. B. JOHNSTON. 
The Optic Chiasma and the Post-optic Commissure. 
This subject has been treated in two papers by Dr. Burron D. 
Myers. In the first’ the chiasma alone was studied by the degener- 
ation method in the toad, cat, dog, rabbit, monkey, owl and snake, the 
toad receiving the most thorough treatment. In the toad certainly and 
probably in the owl and snake the decussation in the chiasma is total. 
In the dog, cat and monkey the decussation is unquestionably partial. 
In the second paper’ the same author makes a more thorough 
study of the relations in the rabbit, using the method of v. GUDDEN. 
The optic nerves and tracts do not begin to become medullated until 
twelve hours after birth; accordingly enucleations of the eye made 
during the first day will result in total failure of medullation of the cor- 
responding optic nerve fibers and very clear pictures can be secured by 
the WEIGERT method, the animals having been killed at various inter- 
vals after the operation. 
The experiments show conclusively that the chiasma of the rabbit 
is partial, though the uncrossed fibers are few in numher. The rela- 
tion of the optic fibers to the post-optic or inferior commissure can be 
determined by reason of the fact that the optic nerves become medul- 
lated earlier than the commissure. Comparisons of series of different 
ages made after enucleation of both eyes with similar series made after 
the enucleation of one eye permits an accurate study of the relations of 
the optic tracts to the commissure. In brief, three such commissures 
are recognized : ; 
1 The Chiasma of the Toad (Bufo lentiginosus) and Some Other Vertebrates. 
Zeits. f. Morph. u. Anthropologie, LLY ..225/ 1901. 
2 Beitrag zur Kenntniss des Chiasmas und der Commissuren am _ Boden 
des dritten Ventrikels. Archiv f. Anat. u. Physiol. Anat. Abt., 1902. 
