Vice-President’s Address. abil 
so with the other areas. If, however, not a macacus or other 
ordinary monkey, but the more highly-developed orang- 
outang be taken as the subject of experiments, the differentia- 
tion is found to be distinctly advanced; the several areas are 
more sharply defined, and what is important to note, the 
respective areas tend to be separated from each other by 
portions of cortex, stimulation of which gives rise to no 
movement at all” (Foster, “A Text-Book of Physiology,” 
5th edition, pt. iii, p. 1043). 
It is of course impossible to repeat these experiments on 
man, but they have unquestionably given an immense 
impetus to the clinical and pathological investigation of 
injuries and diseases of the human cerebral cortex, and it has 
been abundantly demonstrated that similar motor centres 
exist in man. The application of these facts to the treat- 
ment of injuries and diseases of the cerebral cortex by 
Macewen, Horsley, and others, constitute one of the greatest 
triumphs of modern surgery. 
In the remarkable address which Professor Macewen 
delivered at the annual meeting of the British Medical 
Association in August 1888, numerous cases were shown in 
which the exact seat of a lesion in the cerebral cortex had 
been diagnosed and successfully treated. 
There are few questions in morphology that can equal in 
scientific and practical interest those connected with the 
determination of the relation between the cerebral fissures 
and convolutions in man and the higher apes, and I propose 
now to briefly consider some of the more important results 
that have been arrived at from a study of their comparative 
anatomy. We have seen that in 1854 Gratiolet figured the 
brains of the chimpanzee, orang, and gibbon, and he came to 
the conclusion that, not only the main lobes and fissures of 
the human brain were represented in these apes, but also all 
the principal convolutions and secondary fissures; the main 
peculiarity of the human brain being a more convoluted 
arrangement of the individual convolutions, and an increase 
in the number and complexity of the “plis de passage,” or 
bridging convolutions. These bridging, or annectant, con- 
volutions are especially well developed between the parietal 
