579 
of Edinburgh^ Session 1865-66. 
wanting ; that the second is present, but concealed under the opercu- 
lum of the occipital lobe; that the third and fourth are superficial. 
In his comparison of the brain of the Chimpanzee with the brain 
of the Orang, he attaches great importance to the absence of the 
first bridging convolution in the former, and to its presence in a 
well-marked manner in the brain of the latter ape. In his general 
resume (p. 98) of the mode of arrangement of the second bridging 
convolution in the brains of the monkeys of the old world, he states 
that in them it is constantly concealed under the operculum, and 
never comes to the surface ; whilst the third and fourth connecting 
convolutions are always superficial. 
All anatomists who have inquired into this subject since the pub- 
lication of M. G-ratioleCs memoir agree with him in recognising the 
superficial position of the third and fourth, and the concealment of 
the second bridging convolution within the perpendicular fissure in 
the brain of the Chimpanzee. But with regard to the complete 
absence of the first bridging convolution in the brain of this ape, 
evidence has been advanced which proves that M. G-ratiolet’s state- 
ment, although correct in some specimens — as, for example, in the 
one which he described and figured— yet is not universally appli- 
cable. 
Thus Professor Kollesto'n states* that on the right side of the 
Chimpanzee’s brain, in the Oxford University Museum, a well-marked 
superior bridging convolution came, for a considerable part of its 
length, nearly or quite to a level with the lobes it connects ; and 
Professor Marshall describes f on the right side of the brain of a 
Chimpanzee, which he dissected, a rudimentary superior connecting- 
convolution of very small size passing from the outer margin of the 
lobule of the second ascending convolution outwards, and then 
bending inwards and backwards across the perpendicular fissure to 
join the occipital lobe. 
Whilst dissecting the brain of a young male Chimpanzee, which 
was given to me about two years ago by my former pupil, Mr 
Alfred Pullar, I obtained evidence of a greater extent of variation 
in the arrangement of the convolutions in this ape than had up to 
that time, I believe, come under the notice of anatomists. This 
Natural History Review, 1861, p. 211. 
t Natural History Review, 1861, p. 309. 
