500 Dr Duckworth, Report on the brain, etc. 
has just been made, many valuable records are preserved of early 
descriptions of microcephalous and asymmetrical cerebra. 
The last case to which I shall refer is that described (in 
a highly instructive paper) by Dr Turnbull {Brain, Vol. xxvii., 
1904, pp. 209 et seq.). 
The brain in question presented bilateral loss of postcentral 
cortex, but the writer is careful to point out that the case was not 
one of porencephaly, but was rather due to hydrocephalus. The 
attenuation of the cortex consequently produced was so extreme 
that the occipital ends of the hemispheres were transformed into 
mere thin-walled cysts. Associated therewith, Dr Turnbull found 
certain conditions which he regarded as secondary to the primary 
changes wrought by hydrocephalic distension. These so-called 
secondary changes involved the remaining cortex, the corpus 
callosum (splenium), and in particular the optic nerves and their 
central connexions. In all these parts atrophic change was de- 
tected, though, without desiring to criticise Dr Turnbull’s con- 
clusions, I may note that he appears to have detected marked 
deficiency in the number and size of fibres in various regions, 
but not definitely degenerated tracts. 
While recognising the essential difference between this case 
of hydrocephalus, and that of porencephalus described by myself, 
I have been much struck with the similarity in the parts charac- 
terised by their diminutive size in the two brains. In both, 
the corpus callosum (especially the splenium) was abnormally 
small : in both, the external geniculate bodies were either absent 
or of insignificant size : in both, the optic nerves were unduly 
small. These changes Dr Turnbull attributes to the primary 
lesion which, in his case, is that of the postcentral cortex. But 
great as is the similarity in the parts affected, nevertheless in 
the example now described, I do not feel able to assign to these 
changes in the splenium, external geniculate body and optic 
nerve, a corresponding origin, i.e. one secondary to the primary 
cortical lesion. In my example, the asymmetry and the micro- 
cephalic conditions complicate the problem. And to these I prefer 
to ascribe a common origin with the dwarfed condition of the optic 
nerve, &c., to which I have just referred. This common origin 
seems to consist in an impairment of the capacity of part of the 
central nervous system to attain the normal adult status. 
