THE MEDULLA OBLONGATA AND BRAIN. 229 



quadrigemina, the thalamus opticus, the corpus striatum, and 

 the nucleus dentatus. They are only imperfectly known. 



The crura cerebelli ad corpora quadrigemina simply pass 

 oft" beneath the corpora quadrigemina. They pass to the 

 hemispheres of the cerebrum ; they are in truth the crura 

 cerebelli ad cerebrum. The histological acquisitions in this 

 department remain, up to the present time, scarcely worth 

 mentioning. Small cells, larger multipolar, and spindle- 

 shaped ganglion bodies have been met with here. 



The thalamus opticus has likewise yielded nothing further 

 in a histological direction. A portion of the optic nerve 

 radiates into it, as well as into the anterior corpora quadri- 

 gemina. The cap of the crus cerebri is intimately connected 

 with the thalamus (Meynert). 



Fibrous masses of the basal portions of the cerebral 

 peduncles are said to terminate in the corpus striatum and 

 nucleus dentatus. Their finer structure likewise requires more 

 accurate investigation. 



The so-called rod corona fibres, in their great development 

 in man, are probably connected with his mental abilities. 



They consist in the first place of fibrous masses which, 

 without having been in contact with the cerebral ganglia, are 

 conducted upwards through the peduncle of the brain, and 

 secondly of the radiations of the ganglionic substances. 



The trabeculae and anterior commissure are probably true 

 simple commissures, which have nothing to do with either 

 the crura cerebri or these rod-corona fibres. 



The white substance of the hemispheres consists essentially 

 of medullated nerve fibers, measuring 0.0026 to 0.0067 mm. 



The gray cortical stratum of the hemispheres may be 

 reduced to a number of single layers. They may be assumed 

 to be six in number. 



Smaller cells occur in the more superficial layers. In the 

 fourth layer one meets with considerable many rayed gan- 

 glion bodies, measuring 0.025 to 0.040 mm. One of their 

 processes is usually directed tow r ards the surface, and three 

 others inwards. The central one of these three basal pro- 



