196 Royal Irish Academy. 



pronounce an independent judgment on any disputed point respecting 

 it. If I venture to indicate the range of Dr. Cunningham's researches 

 and some of the most important conclusions at which he has arrived, it is 

 because the excellence of his method and the luminous nature of his 

 exposition have made it possible for me to follow him, where with a 

 less able guide I should have failed to make my way. 



As Dr. Cunningham says at the outset, " the descriptive anatomy 

 of the adult human cerebrum is now very nearly complete," and 

 " what still remains to be done is the establishment of our know- 

 ledge on a proper morphological basis." Now the bigher research to 

 which he thus points embraces two studies— first, that of the develop- 

 ment of the surface of the human cerebrum from the early embryonic 

 stages up to mature life ; and, secondly, the comparison of the human 

 cerebrum both in its constituent parts and in their gradual modifications 

 with the simian cerebrum, especially in the anthropoids; in other 

 words, the study of evolution and of anatomical comparison — or, as 

 they are now sometimes called, ontogenetic and phylogenetic research. 

 Neither of these studies, of course, is new ; but to both. Dr. Cunningham 

 has made large contributions. Taking some of the most important cere- 

 bral fissures, first those which are temporary, and afterwards, in suc- 

 cession, the Sylvian, the Eolandic, the intraparietal, and those of the 

 frontal lobes, he examines the history of their formation, and, as 

 illustrated thereby, the growth of particular areas of cortex ; and 

 then the change of position on the surface which those fissures, or 

 some of them, undergo after they have been once laid down. 



The special features of his mode of investigation are these : — 1, 

 the brain is hardened in situ, instead of being first removed from the 

 cranial cavity ; and 2, the measurements he makes on the surface are 

 not absolute, but relative to the mesial length of the hemisphere, and 

 he is thus enabled to fix corresponding points in brains of different 

 sizes and at different stages of growth. 



In man, except in abnormal cases, the complete fissures on the 

 outer faces of the hemisphere have, in general, only a temporary 

 existence during an early period of development ; as the cerebral growth 

 proceeds, they are obliterated, and leave the surface again smooth. 

 Some of the complete fissures on the mesial face of the hemispheres are 

 retained, in whole or part, in the adult cerebrum ; there is much 

 interesting matter in the Memoir relating to these, on which, however, 



