vin THE HIND-BKAIN 455 



there was an associated atrophy of certain systems of fibres of the 

 cord and bulb. 



VI. As long ago as 1879 Nothnagel pointed out that the 

 symptoms of disease of no other part of the brain are so uncertain 

 as in the cerebellum. Even to-day loose, inaccurate, and con- 

 tradictory clinical observations only tend to make any general 

 conception of the functions of the cerebellum difficult. The 

 reasons for this failure of clinical and experimental observations 

 to agree are numerous, and must be understood by the physiologist 

 who wishes to avail himself of clinical observation. 



In the first place, the material for clinical observation of 

 diseases of the cerebellum is not plentiful. In 1899 Adler 

 published a brief review of 124 of the best observed cases from 

 the literature of the ten years preceding. To this survey we need 

 only add the few cases published between 1898 and the present 

 day. . 



In these statistics cases of tumours of various kinds pre- 

 dominate largely over all other forms of disease ; atrophy and 

 agenesia are less frequent ; still less common, haemorrhagic foci, 

 softening, abscesses ; rarest of all, traumatic and surgical lesions. 



A highly important fact which impresses every one who 

 studies clinical cases of cerebellar diseases is that in some of them 

 the disease remains obscure or latent during life and is not 

 suspected before the post-mortem examination. Our Monograph 

 of 1891 showed that certain of the cases described as "latent" 

 were so only to the extent that the accentuated form of dysmetria 

 of movements which many of the older and some of the modern 

 clinicians hold erroneously to be the most characteristic sign of 

 cerebellar disease, and which are fallaciously termed " disturbances 

 of co-ordination " were wanting. But in other cases there could 

 be no doubt that the le'sions of the cerebellum - presented no 

 symptoms. 



If these cases of comparative or total absence of the essential 

 phenomena of cerebellar deficiency are investigated one by one, it 

 will be found that they are all instances of agenesia, viz. a more 

 or less complete congenital defect or arrested development of the 

 organ, dating back to embryonic life, or of sclerosis or atrophy, 

 which are the final outcome of circumscribed encephalitis with a 

 slow course. 



Mingazzini has recently made a fresh investigation of all the 

 earlier and recent cases of agenesia and atrophy of either half 

 or the whole of the cerebellum, and came to the following con- 

 clusions : 



(a) Agenesia of half the cerebellum usually runs its course 

 without any symptoms whatsoever. 



(6) Unilateral cerebellar atrophy remains latent, when only 

 the superficial cortex is affected. 



