No. 1.] AMPHIBIAN BRAIN STUDIES. 89 
. of his histological methods his observations were fragmentary; second, because the 
brains of Rana and Cryptobranchus differ so widely. 
Stieda designates asthe nucleus centralis the group of sensory cells in the 
floor of the ventricle on either side of the sulcus centralis. I cannot support his 
suggestion that this nucleus is in any way connected with the Vagus roots. As he 
has confused the Facial and Auditory nerves and nuclei, his results, so far as these 
are concerned, are invalidated. 
K6éppen, profiting by the Weigert method, has given a much more precise and 
full description of the mzedudla, although his description of the Facial-Trigeminal 
system is very incomplete. 1. He recognizes the posterior longitudinal 
fasciculus, p. 6, and its probable connection with the Auditory nerve. This 
adjoins the dorsal part of the Miillerian fibre system, the ventral part of which, 
after crossing, disappears, as in C7yftobranchus, in the great ganglion cells oppo- 
site the exit of the Auditory nerve. 2. He describes also, p. 7, a nucleus of 
large cells as probably belonging to the Auditory; this corresponds to my pale 
ganglion, 8, Fig. 14. At this point he fails to distinguish between the Facial 
and Auditory elements, for his dorsal Auditory root, p. 9, is probably the main 
portion of the Facial. This error, if error it be, arises from the fact that he expects 
to find the facial a purely motor nerve, p. 10. 3. The Trigeminus, p. 10, is traced to 
two ascending bundles, and a large motor nucleus. No sensory nucleus or mesen- 
cephalic descending bundle is described. 4. Képpen makes many important addi- 
tions to the higher encephalic tracts and nuclei in Rava, among which are the 
Auditory tract to the cerebellum, p. 13; the interpeduncular ganglion, p. 16; the 
posterior longitudinal fasciculus to the region of the III nucleus, p. 17; the infundi- 
bular tract to the hemispheres; the mesencephalic and diencephalic tracts from the 
medulla, and the tracts from these segments to the hemispheres, pp. 30-31; the 
ganglion habenulz and Meynert’s bundle. The hemispheres receive no direct sen- 
sory tracts from the medulla; these tracts first enter the optic lobes and thalami, 
from which fresh tracts rise to the hemispheres. With this conclusion, p. 31, I am 
inclined to agree, although I do not think it is absolutely demonstrated. 5. I differ 
from Képpen in his attempt to homologize the encephalic with the lower segments, 
p- 26; also, as I understand him, p. 30, he does not describe any direct motor tract, 
(basal forebrain bundle), to the anterior columns of the medulla. The agreement, in 
respect to the tracts mentioned above, is strongly confirmatory, since my observations 
were made independently, and the conclusions reached before the receipt of his 
paper. 
6°. Methods. The methods of hardening and staining have been fully de- 
scribed in previous papers. The best staining results have been obtained with long 
zz toto immersion in Ammonia Carmine. I have had the advantage, for purposes 
of comparison, of a full series of the brain of Sa/amandra, prepared after Weigert’s 
Method by my assistant, Mr. J. Warne Phillips, in Dr, Edinger’s laboratory. I 
find that brilliant as these preparations are, the carmine series give a fuller and more 
reliable field of observation. The late Professor Gudden, of Munich, told me, after 
long experience, that he had reached the same conclusion, and this is also the 
opinion of Dr. Spitzka of New York. 
