Herrick, Nerviis Terminalis of Frog. 179 



sphere on one side. Neither the fila olfactoria nor the fibers of 

 the nervus terminalis are stained, and therefore the peripheral rela- 

 tions cannot be determined. The nervus terminalis (unstained) is 

 seen to detach itself from the olfactory nerve under the olfactory 

 bulb and to pass back to the lamina terminalis exactly as already 

 described. Within the brain it is surrounded by a dense mass of 

 deeply stained fibers belonging to the secondary olfactory and other 

 systems, so that it can easily be followed back to its decussation as 

 a clear yellow area surrounded by a dark field of impregnated 

 fibers. 



Professor J. B. Johnston informs me that in 1905 he observed 

 a similar nerve in Golgi sections of the adult frog brain; but since 

 he had no control of this single observation, it was not published. 



In the Golgi sections of the young larva (Figs. 9 and 10) the 

 nervus terminalis is seen to enter the lamina terminalis and there 

 its fibers arborize, some of the free termini crossing the meson and 

 some remaining uncrossed. Other histological preparations of the 

 larva show that the cells in the region of these arborizations are 

 much crowded, forming the nucleus medianus septi. It is probable 

 tliat in the adult also the nerve ends in the nucleus medianus septi, 

 either wholly crossed or partly crossed and partly direct, as in the 

 tadpole. 



In the horizontal series of sections through the brain of an old 

 larva of Rana catesbiana stained with hsematoxylin and crythrosin 

 very nearly the whole intra-cerebral course of the nervus terminalis 

 is sho^\m in four consecutive sections, as seen in Fig. 8. The 

 nucleus medianus septi does not appear here. It lies immediately 

 dorsally of the plane figured as a dense mass of cells which crosses 

 the median plane in the lamina terminalis directly ventrally of the 

 foramen of Monro. 



The relations of the nervus terminalis of the larva are essentially 

 similar, so far as observed, to those of the adult frog, save that the 

 nerve enters the brain relatively farther rostrad and farther laterad 

 in the larva. Fig. 8 shows it penetrating the formatio bulbaris 

 rostrad of the l:)ulbulus accessorius. It seems probable to me that 

 the point of entrance of the nervus terminalis remains relatively 



