184 Journal of Comparative Neurology, 



method in which the sections- are in the horizontal plane I find 

 fibers above it on each side of the brain that seem to run 

 down to and join it in its middle portion. But in bichromate ol 

 silver preparations, although I have several times found some of 

 its fibers impregnated I have not found sufficient evidence to 

 warrant my saying that it branches. Just where its cells of or- 

 igin are I have not been able to determine. 



THE DORSO-CEREBRAL COMMISSURES. 



Of the bands of fibers connecting the two lateral halves of 

 the dorso-cerebron there are at least six, and of these two have 

 already been noted in connection with the optic tracts. Some 

 of them have long been known, but on account mostly of a 

 lack of proper neurological methods have seldom been correctly 

 understood. Viallanes (87, SS) seems to have made fewer mis- 

 takes than any other writer who has considered them. 



TJie Superior Dorso-cercbral Coinvnssnre. 

 This band of fibers crossing the median line of the brain 

 above the central body and between the two inner stalks of the 

 mushroom bodies (fig. 2) was noted by Dietl ( 70) and Ber- 

 ger ( 78) and considered as connecting the two optic lobes, a 

 mistake perpetuated by Bellonci in his study of Grylotalpa. 

 The fibers are brought out very prominently by most of the or- 

 dinary methods and I have repeatedly found them impregnated 

 in brains treated by the bichromate of silver method. They 

 are all of small size and non-medullated. By a comparison of 

 frontal and horizontal sections (figs. 2 and 7) they are seen, to 

 form a band whose broadest extent is in the antero-posterior di- 

 rection, and to be divided at either end into two parts — a divis- 

 ion that can sometimes be distinguished throughout the length 

 of the commissure — one of which passes behind and the other 

 in front of the stalk. There does not seem to be a crossing of 

 the fibers, but those passing in front of one stalk also pass in 

 front of the other. In preparations with heematoxylin or 

 with osmic acid the halves may be traced in horizontal sections 

 around the inner stalks to the space between these and the outer 

 ones and apparently into the calices. Since the tracts from the 



