A CONTRIBUTION), TO) THESINEERNAL. STRUC-= 
TURE OF THE AMPHISIAN) BRAIN. 
PROF. HENRY FAIRFIELD OSBORN, 
PRINCETON COLLEGE. 
INTRODUCTION. 
Tuis contribution to the structure of the Amphibian brain is 
the result of observations which began in 1879 and have ex- 
tended at wide intervals over several years. The most syste- 
matic of these studies, beginning in Munich in 1886, were 
directed to the nerve-fibre courses, and interrupted by the dis- 
covery of the corpus callosum, which naturally led off to the 
comparative study of the encephalic commissures in the verte- 
brata. They form the chief portion of the present paper, and 
have long been withheld from publication in the hope that an 
opportunity would arise to make them more thorough. As this 
seems now more distant than ever, it appeared to me best to 
publish them in their present shape, with the intention of attach- 
ing to each new point the degree of certainty to which the evi- 
dence entitles it. Only by carefully distinguishing between 
fully and partially established facts can a contribution of this 
unfinished character acquire any permanent value. The most 
carefully observed region is the medulla oblongata of C7rypto- 
branchus, with reference especially to the cranial nerve tracts and 
nuclei. The structure of the cerebellum in the Uvodela has been 
well worked out, also the region of the optic lobes, thalami, and 
posterior portion of the hemispheres in the Urodela and Anura. 
Much remains to be done in respect to the peripheral distribu- 
tion of the component parts of the several cranial nerves. Only 
after this has been thoroughly worked out can we certainly deter- 
mine the homologies of the cranial nerves and their segmental 
relations in the Amphibia. The present results go far enough 
to show that the determination of definite nuclei corresponding 
to definite peripheral sensory and motor areas is well within the 
range of possibility. In fact, the provisional character which I 
have given to some of the conclusions here reached is chiefly 
