BRAIN OF MAN AND THE BRAINS OF CERTAIN ANIMALS. 27 



alone, and not with the intra-cranial masses which they overlie, 

 that we shall have to deal when contrasting the human with the 

 simious and other animals, for it is in them that we find more 

 marked differences existing- than elsewhere in the entirety of the 

 softer parts of the compared organisms, and it is in them that we 

 should anticipate the finding of such differences from what we all 

 know of the correlation subsisting between mental phenomena and 

 the greater or less evolution of these structures. And, secondly, 

 though less attention has been paid to any differences which may 

 exist between the rest of the intra-cranial nerve stem — between the 

 spinal cord and the peripheral nerve-ramifications throughout the 

 body in the two sets of organisms to be compared — that less atten- 

 tion has nevertheless been sufficient to show that these differences 

 are of infinitely less moment than those which a comparison of the 

 cerebral hemispheres enables us to elicit. 



We will commence with a description of the interior of the cavity 

 included within the cerebral hemispheres which we shall have to 

 compare, and proceed, in the second place, to contrast their external 

 surfaces in their simple outlines and in their complex convolutions ; 

 we will conclude by stating the differences which measures show to 

 exist between the connecting floors, and weights show to obtain 

 between the entire mass of the intra-cranial nerve-centres in the 

 one and in the other set of organisms. 



The question as to the difference between the human ventricular 

 cavity and that of the ape's may be thus stated, — Has the ape such 

 a ventricular cavity tri-radiate, three-horned, as has the man ? or 

 has it a ventricular cavity bi-radiate and two-horned, as has the 

 dog ? The two-horned ventricle of the dog is seen in figure I «, ex- 

 posed in the interior of the right hemisphere. The ventricular 

 cavity of the African vervet monkey is shown in figure i h ; the 

 ventricular cavity of the American marmoset in figure %, It 

 is clear enough that the African monkey has that which the 

 dog has not, that the former animal has a horn-shaped, finger- 

 shaped creek, turning up into what is in the dog a solid unindented 

 mass. That horn, finger, creek-shaped cavity was in the monkey 

 f" in length, the entire length of its brain being little (tV) over 

 2 J inches ; the analogous, or homologous cavity in the human 

 brain was i" in length, §" longer than the vervet's, albeit its 

 hemispheres were 6}" as against 2 J". In the American monkey 



