26 ON THE AFFINITIES AND DIFFERENCES BETWEEN THE 



the French speak of as c consequences desastreuses, funestes pour 

 la morale/ The susceptibilities of no one, therefore, need be 

 offended by his being told that he must necessarily take up for 

 himself one or other of these four sets of dogmas, unless he be con- 

 tent to put himself into the somewhat inert position of passively 

 receiving the facts, and drawing no deductions from them. I must 

 add, that I cannot see that the holding of any one of these four sets 

 of opinions is necessarily incompatible with a belief in the details 

 I shall have to lay before you. Stubborn as are facts, especially 

 when photographed, they are nevertheless elastic enough to bear 

 being compressed within any one of these four formulae without 

 losing their own distinctive character, or destroying the framework 

 employed for their colligation. That these four theories are all 

 true together, of course I do not mean to assert; three of them 

 must, in the very nature of things, be erroneous ; but I do think 

 that, to be assailed successively, they must be attacked with other 

 weapons than any which anatomy, whether human, simious, or 

 canine, can furnish. 



The cerebro- spinal system of the vertebrate animal consists of a 

 central stem and of peripheral ramifications. Of the peripheral 

 ramifications we are not about to speak, and of its central stem we 

 shall only compare that part in each of the subjects of our com- 

 parison which is contained within the cranial walls. This part of 

 the cerebro-spinal centre, like the other part contained within the 

 canal constituted by the spinal column, is essentially — that is to 

 say, morphologically and developmentally — as well as actually in 

 the adult state, but a hollow tube with walls of nerve matter. 

 These walls are variously thickened, have larger and smaller nodules 

 of nerve substance developed in, around, and upon them, and finally, 

 their exterior surface becomes more or less completely corrugated 

 into convolutions. Still the essential nature of the nervous centre 

 remains within the skull, the same as within the column of ver- 

 tebrae, viz. a nervous tube. The difference between the intra- 

 cranial and the intra-spinal nerve tube is, that the intra-cranial 

 effloresces or buds out at its upper or anterior extremity into two 

 out-growths, which are folded back upon it as they grow out, and 

 expand into the nerve masses which, under the name of Cerebral 

 Hemispheres, fill by far the larger part of the skull cavity. It is 

 with these terminal dilatations of the hollow central nerve stem 



