October 18, 1901.] 



SCIENCE. 



607 



making this statement it is right to add 

 that Hochstetter, in a carefully reasoned 

 memoir, has recently cast doubt upon the 

 reality of the appearances which have led 

 to this conclusion, and at the recent meet- 

 ing of the Auatomische Gesellschaft, in 

 Bonn, Professor Gustaf Ketzius,-!'^ one of the 

 numerous observers responsible for the 

 description of the early cerebrum upon 

 which the conclusion is based, showed some 

 inclination to waver in his allegiance to the 

 old doctrine. This is not the time nor the 

 place to enter upon a discussion of so tech- 

 nical a kind, but I may be allowed to say 

 that whilst I fully recognize the necessity 

 for further and more extensive investigation 

 into this matter I do not think that Hoch- 

 stetter has satisfactorily accounted for all 

 the circumstances of the case. 



When the occipital lobe assumes shape 

 the relationship of the cranial wall to 

 the enclosed cerebrum undergoes a com- 

 plete change. The cranium expands so 

 rapidly that very soon a wide interval 

 is left between the surface of the cerebrum 

 and the deep aspect of the cranial envelope 

 within which it lies. This space is occu- 

 pied by a soft, sodden, spongy mesh work, 

 termed the subarachnoid tissue, and it is 

 into the yielding and pliable bed thus pre- 

 pared that the convolutions grow. At first 

 the surface of the cerebral hemisphere is 

 smooth, but soon particular areas of the 

 cortex begin to bulge out and foreshadow 

 the future convolutions. These suffer no 

 growth restriction, and they assume the 

 form of round or elongated elevations or 

 eminences which rise above the general 

 surface level of the cerebral hemisphere and 

 break up its uniform contour lines in the 

 same manner that mountain chains pro- 

 trude from the surface of the globe. 



As growth goes on, and as the brain 



* Anatomisehe GeseUschaf (, Bonu, May 28, 1901. 

 Gnstaf Retzius, ' Transitorische Furcben des Gross- 

 hirns.' 



gradually assumes a bulk more nearly in 

 accord with the cavity of the cranium, the 

 space for surface protrusions of this kind 

 becomes more limited. The gyral eleva- 

 tions are now pressed together ; they be- 

 come flattened along their summits, and in 

 course of time they acquire the ordinary 

 convolutionary shapes. While this is going 

 on the valleys or intervals between the 

 primitive surface elevations become nar- 

 rowed, and ultimately assume the linear 

 slit-like form characteristic of the fissures. 

 These changes occur shortly before birth, 

 but are not fully completed until after the 

 first few months of infancy. The final re- 

 sult of this process is that the convolutions 

 come into intimate relation with the deep 

 aspect of the cranial wall and stamp their 

 imprint upon it. 



It is obvious that certain of the later 

 changes which I have endeavored to por- 

 tray might be ascribed to a growth antago- 

 nism between the brain and the enclosing 

 cranium at this period. In reality, how- 

 ever, it is merely a process by which the 

 one is brought into closer adaptation to the 

 other — a using up, as it were, of superfluous 

 space and a closer packing together of the 

 convolutions — after the period of active 

 cortical growth is past. Nevertheless the 

 convolutionary pattern is profoundly af- 

 fected by it, and it seems likely that in this 

 process we find the explanation of the dif- 

 ferent directions taken by the cerebral fur- 

 rows in brachycephalic and dolichocephalic 

 heads. 



The cortical elevations which rise on the 

 surface of the early cerebrum are due to 

 exuberant growth in localized areas. There 

 cannot be a doubt that the process is inti- 

 mately connected with the development of 

 function in the districts concerned. We 

 know that functions of different kinds are 

 localized in difi"erent parts of the cortex, 

 and when we see an area on the surface of 

 the early cerebrum rise up in the form of 



