6 ON THE AFFINITIES OF THE BRAIN 



internal viscera presented any appearance of disease. The lungs, 

 which were both but unilobar, were crepitant throughout, free from 

 congestion, collapse, or tubercle. 



The callosities on the backs of the fingers, which have been held, 

 and with some show of probability, to indicate the existence of a 

 state of debility, were absent. 



The roof of the cranium was removed by a circular incision, 

 intersecting the foramen magnum posteriorly. Before the removal 

 of the dura mater the cerebral hemispheres w 7 ere seen to cover the 

 superior surface of the cerebellum entirely, and even to project a 

 very little way beyond it posteriorly. After the removal of the 

 dura mater a small segment of cerebellar surface became visible on 

 each side, posteriorly to the tips of the occipital lobes. It is well 

 known x that the antero-posterior dimensions of the corpus callosum 

 are very different in a brain whilst contained and supported within 

 its case, and when removed from the skull— the forward swaying 

 of the hemispheres upon their supporting stems, the crura, flatten- 

 ing the previously arched commissure. That it was the weight of 

 the hemispheres, working similarly, which produced the alteration 

 just noted in the relations of the cerebrum to the cerebellum was 

 seen thus — a wider segment of cerebellar surface was visible on the 

 left side than on the right, the animal lying over towards its right side. 



The greater width of the semi-lunar segment exposed on the left 

 side was no doubt owing to the gravitation of the cerebral lobes, 

 but the greatest width of this segment was only three lines. The 

 relations thus described are well shown in PI. iii. Fig. 3. The view 

 of the base of the brain, as given in Fig. 2, will enable us to com- 

 plete our observations as to the relations of the cerebellum to the 

 posterior lobes of the cerebrum. On looking at that figure it will 

 be seen that no cerebral surface comes into view on the outside of 

 the lateral boundaries of the cerebellum. In a view of the base of 

 the human brain, some cerebral substance is invariably seen in this 

 situation; but the same is the case with a second orang's brain, with 

 a chimpanzee's brain, and with the brains of several Cercopitheci, and 

 an Inuus, in the series belonging to the Christ Church Museum. 



1 ' Bei der Messung der Lange des Balkens muss man wohl im Auge behalten dass 

 man ihn misst so lange die Hemispharen ihre Lage noch in Schadel haben ; am heraus 

 genommenen Gebirn dehnt er sich sehr betrachtlich in die Lange aus und verliert seine 

 Wolbung.' Huschke, 'Schadel, Hirn und Seele/ p. no. 



