THE PONS AND THE CEREBELLUM. 145 



and covered in by fibres which, originating in the horizontal 

 branch of the arbor vitse, connect the two decussating commis- 

 sures, and in part pass off to the cerebellar hemispheres with 

 the fibres of the anterior of these commissures. The nuclei 

 tegmenti are connected with all these fibres. 



The external surface of the cerebellum was described by Malacarne, Reil, 

 and Burdach, just as it is described to-day. Investigations of its internal struc- 

 ture were undertaken by F. Arnold, Reil, Kolliker, Meynert, and particularly by 

 B. Stilling. Later researches as to the structure of the peduncles have been made 

 by Bechterew, Marchi, and the author. A whole literature has been written on 

 the cortex of' the cerebellum, among the contributors to which are Purkiuje, 

 Gerlach, Hess, Kolliker, Fee, Schultze, Obersteiner, Beevor, and Golgi. 



Diseases of the cerebellar peduncles alone are very seldom 

 observed. For this reason we are not familiar with the symp- 

 toms which would be caused by them. Gradual destruction of 

 one brachium pontis may, apparently, give rise to no symptoms. 

 Diseases which cause irritation (hemorrhage, for example) may 

 bring about forced movements, generally of a rolling nature, 

 now toward the affected side, .and now toward the sound one. 

 A forced position of the trunk or of the head only, with or with- 

 out nystagmus, has been observed in irritating diseases of one of 

 the peduncles. 



Diseases of the cerebellum may, on account of the inti- 

 mate association with and proximity of the complex tracts of 

 fibres lying in the crura cerebri, the pons, and the medulla ob- 

 longata, give rise to symptoms which cannot be attributed to the 

 cerebellum. In cases where only actual cerebellar substance is 

 diseased, we find vertigo, headache, vomiting, uncertainty of gait 

 (ataxy), and vague feelings of weakness in the extremities, both 

 of the same and the opposite side. Real paralysis and sensory 

 disturbances are wanting. Occasionally, vision is seriously 

 affected; still, it is difficult to say how far this may depend on 

 a participation of the visual centres near by. Mental disturb- 

 ances often appear in disease of the cerebellum. Inasmuch as 

 many diseases of the cerebellum present no symptoms, and none 



of the symptoms above enumerated are caused exclusively by 



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