Literary Notices. xv 



paresis of a function without having the paralysis of a well defined 

 muscular group. 



The author promises to extend these studies to other animals also, 

 especially to the monkeys. 



G. F. MC KIBBEN. 



Jfew Studies on the Pons Varolii.^ 



The methods of Golgi and Weigert applied to the dog, the cat, 

 the Guinea pig, the mouse and the white rat led to the following con- 

 clusion about the pons. 



I. The pons is the place of origin for the greater part of the 

 fibres constituting the middle cerebellar peduncles ; these fibres pene- 

 trate the white substance of the cerebellum and then go into the cor- 

 tex of the cerebellar lamellae, where they consitute perhaps the as- 

 cending fibres. 



2.. The medulla is also formed by axis cylinders from the cells 

 of Purkinje, which after having crossed the median line and taking a 

 more or less vertical course, direct some longitudinal fibres into the 

 reticular substance of the opposite side. 



3. These facts, together with the existence of collaterals in the 

 medulla from the pyramidal tract, throw some light upon the influence 

 of the cerebrum upon the cerebellum. Suppose, for example, that 

 the cerebrum sends along the pyramidal tract a voluntary motor im- 

 pulse to the muscles. This impulse, having reached the level of the 

 medulla, will pass in part through the pyramidal collaterals and the 

 fibres of bulbar origin up to the cerebellum. There it will excite the 

 cells of Purkinje and those subordinate to them to add to the motor 

 impulse a coordinating nervous current which will reach the motor 

 niduli of the medulla and cord, perhaps by way of the second kind 

 of bulbar fibres, perhaps by the corpus restiforme, or perhaps by the 

 descending cerebellar fibres of Marchi of the antero-lateral columns. 

 From this it results that the cerebellum receives information of every 

 voluntary motor impulse and its cooperation is necessary for the pre- 

 cise execution and coordination of movements. 



4. The pyramidal tract is in connection by means of its collat- 

 erals with different grey centres of the encephalon and cord. For 

 example, with the cells of the striata through the collaterals of the 

 small fibres of the internal capsule; with the substantia nigra of Soem- 

 mering through other collaterals from the superior part of the pedun- 

 cles, with the cells of the pons and consequenrly with the cortex of 



^Cajal, S. R. Le Pont de Varole. Bibliogr. Anat., II, 6 Dec, i{ 



