320 ELEMENTARY PHYSIOLOGY. [XXX. 



Note at the posterior part of the optic thalami 

 in the median line the round pineal gland, and 

 running from this near the middle line two 

 thin white bands, the peduncles of the pineal 

 gland, one over the optic thalamus of each side. 

 Between the optic thalami, and running across 

 the third ventricle, is seen the large middle 

 cerebral commissure, of grey substance and 

 hence very readily torn through. 



20. Cut away on one side the cortex so as to 

 completely expose the optic thalami and optic 

 tract, and trace the course of the optic tract, 

 carefully tearing away the pia mater. The optic 

 tract will be seen to curve dorsally and form an 

 eminence, the external corpus geniculatum, 

 at the posterior lateral part of the optic thala- 

 mus; over this may be seen fibres running to 

 the optic thalamus, and a rather large band of 

 fibres curling back and running into the anterior 

 corpus quadrigeminum (the so-called brachium 

 of the ant. corp. quad.). 



21. Below and behind the external corpus genicula- 

 tum a small eminence, the internal corpus 

 geniculatum. 



Both geniculate bodies are more marked in the dog 

 than in the sheep; the position of these bodies is 

 different in man; in man the backward projection of 

 the optic thalamus or pulvinar has the position here 

 occupied by the external geniculate body. 



Disappearing underneath the posterior edge of 

 the internal corpus geniculatum will be seen a 



