( 26 ) 



will differ still more widely regarding llie meaning, in a more 

 restricted sense, of the mesencephalic nucleus, i.e. regarding the 

 periphery organs w^ith wdiich they arc conjiected by their neurones 

 or which organs thej^ ultimately act upon. It even seems useless to 

 discuss these opinions as long as there is no anatomical foundation 

 for them. 



The valuable help of experiments was not even able to throw 

 light on this point. From all investigations results, that a degenera- 

 tion of the cells of the mesencei)lialic quintus-nucleus, if this be 

 not complicated with other lesions, causes no apparent disturbances. 



And in the case of some abnormalities noted during life, which a 

 few observers have connected with a degeneration of the above- 

 named nucleus found on a postmortem examination with other 

 lesions, the dependence from a finictional disturbance of the nucl. 

 mesencephalic, ti-igemini has not appeared to be [)robable (Mendkl, 

 Tooth, Hagpilsta.m, Homkn). 



A pathological ol)servation which I made drew my attention to 

 the question here alluded to, and led to the investigation, the results 

 of which 1 shall give here. ') 



This pathological observation was as follows. A woman had suffered 

 for J 2 years from a subdural haematome behind the right 

 orbita. All the nerves entering the tissui-a orbitalis superior were so 

 pressed by the tumor as to cause ophthalmo[»legia completa dextra 

 and a tyi)ical anaesthesia in the region of the first ramus trigemini. 

 All the other brain nerves were intact, except for a slight facialis 

 paresis of the left side of the mouth of supra-nuclear origin ; in 

 particular the action of the 2'"^ and 3'^^ trigeminus was perfecth' 

 normal. After death a partial degeneration was seen in the 

 right mesencephalic (piintus-i-oot, and a careful counting revealed 

 that the number of its cells, as compared with the left, was 

 reduced to Vs- 



The fibres of the mesenc. root degenerated by the haematome could 

 not find outlet in the motor trigeminus nor in Ram. II or III sens. 

 On the contrary, they were to be looked for either in Ram. I 

 trigemini, or at .least behind the orbita in such a way, that the 

 tumor could have destroyed them. 



This discovery is opposed to the above-mentioned, almost generally 

 accepted, view of a motor function, wdiich localises the mid-brain 

 fibres in the pars motoria. On the other hand, it does not exclude 

 a motor function, although we do not hioiv any trigeminus consti- 



1) A detailed description will appear in the Folia Neurobiologica, 



