1888.] Dr A. Bruce on Absence of Corpus Callosum. 833 
other commissures. A small hyatid cyst, size of hazel-nut, lying 
anterior to corpus quadrigemina, with smaller ones adhering to it, 
containing gelatinous fluid ; small quantity of fluid in ventricles ; 
brain firm. 
3. Cases of Absence of Anterior Part of the Corpus Callosum. 
XXII. Mitchell (Henry), Med. Chir. Trans., xxxi. p. 239, fig. 14. 
— Boy, 15; civil and well conducted; slow in acquiring know- 
ledge at school ; could read and write, hut in doing so had tendency 
to fall asleep ; had difficulty in learning his trade, but was very 
shrewd in money matters ; generally mentally sluggish. Injury to 
head from cricket ball three years before death (confined to hospital 
for 12 months). Brain and convolutions of normal size, skull and 
dura normal, anterior part of body of c.c. absent exposing ven- 
tricles, velum interpositum probably torn through, posterior J of 
c.c. present, measuring IJ inch long, from anterior border to tip of 
frontal lobe = 3 J ; posterior margin 2 inches from tip of posterior 
lobe ; at side of cavity the corpus callosum persists as a thin 
rounded margin. The septa lucida, fifth ventricle, and most of the 
anterior pillars of the fornix were absent ; anterior commissure and 
small part of the anterior pillars of the fornix, and most of the 
posterior part of the fornix were present. The radiating fibres 
from all parts of the corpus callosum seemed normal. Query? Was 
this not a case of dropsy of the fifth ventricle which had caused 
destruction of the anterior part of the c.c., the septa lucida, and 
the corresponding parts of the fornix ? (fig. 14). 
XXIII. Langdon Down, Med. Chir. Trans., xliv. p. 219. — Boy, 
aged 9 ; idiotic, could not stand, or feed himself, or speak ; fond of 
music. Calvarium thick, somewhat unsymmetrical ; brain weighed 
2 lbs. 8 oz. Membrane normal, velum interpositum present, pos- 
terior cornu of ventricles enlarged, positive absence of any septum 
lucidum ; fornix present — its pillars widely separated ; no commis- 
sure of body ; anterior commissure present ; two lines above it a 
transverse band (perhaps a rudiment of the corpus callosum) not 
more than in thickness ; middle soft commissure absent. 
XXIV. Langdon Down, Med. Chir. Trans., vol. xlix., 1886, 
p. 195. — Male, 40. Could read easy words, learning to write a 
little, answer simple questions, fond of music, memory defective. 
