444 



THE PINEAL ORGAN 



sinus between silver clips, and then slit up the lower border of the falx 

 for half an inch or more with a curved tenotomy knife (Fig. 295). The 

 splenium of the corpus callosum is then incised in the midline and the 

 tumour exposed. Any bleeding that may be encountered in this procedure 

 is checked by the diathermy point. The most important structure in 

 relation to the tumour is the great vein of Galen, which lies under the 

 fornix. This vein and its tributaries should be carefully preserved. 



Fig. 293. — The Exposure of the Corpus Callosum. The Ligated Cerebral 

 Veins can be seen as they enter the Superior Sagittal Sinus. 



The tumour is carefully prised out of its bed by means of a curved dis- 

 sector, such as Adson's. It may be that the third ventricle is opened while 

 the tumour is dissected out of its bed, but this does not matter (Figs. 

 294, 296). Absolute hsemostasis is essential, and all bleeding points are 

 controlled by the application of silver clips or the use of the diathermy 

 point. 



The tumour bed must be quite dry before completing the operation. 

 The posterior part of the cerebral hemisphere is allowed to fall back 

 into place, and the dura mater united with one or two tethering sutures. 

 Drainage by means of a fine corrugated rubber dam is often necessary 



