[246 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



observation. Lonsf before the dawn of the scientific 

 era, the cerebellum was recognized as a special por- 

 tion of the central nersous system. However, from 

 the time of Galen through the writings of Thomas 

 Willis, opinion concerning cerebellar functions was 

 based entirely upon speculations, framed in what we 

 now consider to be meaningless terminology and 

 based on the confused concepts of neural function in 

 vogue at any particular time. Nevertheless, Willis' 

 speculative suggestions (364) that the cerebellum 

 controlled such functions as the heart beat, respira- 

 tion and other vegetative functions, led evcntuallv to 

 experimental investigations which, although they 

 refuted his suggestions, have laid the foundations for 

 our present concepts of cerebellar fimction. Discus- 

 sions of this period in the de\elopment of cerebellar 

 physiology may be found in Neuberger (253) and 

 Rawson (278). 



The true nature of cerebellar function began to 

 emerge with the first crude attempts to describe the 

 alterations in beha\ior following the remo\'al of the 

 cerebellum from li\e animals. Through the work of 

 Duverney (115), von Haller {352), Rolando (280) 

 and Flourens (124), the broad outlines of cerebellar 

 influence over the control of motor actisities of the 

 central nervous system were soon laid down. Through 

 the suij.sequent years, the refinements of surgical 

 skill in the preparation of experimental ablations, in- 

 creasing sophistication on the part of clinical ob- 

 servers and the deselopment of new techniques of 

 inquiry have contributed accuracy and precision to 

 the descriptions of cerebellar dysfunctions. The be- 

 ginnings of true understanding, howe\'er, ha\'e only 

 begun to develop on the loackground of the anatomi- 

 cal understanding which has been furnished by the 

 work of comparative and experimental anatomists 

 guided so importantly by Larsell and the workers of 

 the Norwegian school. 



Throughout the earlier portion of the experimental 

 period, several unrecognized difficulties were en- 

 countered by investigators which added measurably 

 to confusion and diflferences of opinion. As is the 

 case with the cerebral cortex, the cerebellum has 

 undergone extensi\e phylogenetic alteration in 

 structure and function. The species differences re- 

 sulting from these alterations were not immediately 

 recognizable. The earlier experimental work also 

 suffered from lack of histological controls of experi- 

 mental procedures. The existence of intracerebellar 

 decussations, the proximity of nuclear and cortical 

 structures, plus the juxtaposition of the cerebellum 

 and important motor control svstems of the brain 



stem, make histological controls mandatory in any 

 experimental study of the cerebellum. Much of the 

 earlier experimental work is impossible to interpret 

 with any degree of assurance because of the absence 

 of such controls. And finally, the ability of experi- 

 mental animals to compensate for experimentallv- 

 produced cerebellar deficits introduces an important 

 time factor into experimental studies involving 

 chronic cerebellar lesions which was not taken into 

 consideration in much of the work of the nineteenth 

 and early twentieth centuries. The student of the 

 original literature on cerebellar physiology should 

 bear these points in mind in exaluating the reports 

 which he reads. 



.\N.^TOMIC.-\L ORIENT.JiTION 



It is unnecessary here to consider the anatomical 

 relations of the cerebellum in detail. For exhaustixe 

 treatment of this important subject the reader is 

 referred to Larsell (181) and to [ansen & Brodal 

 (169). 



Gross Morphology 



The purely functional aspects of the cerebellum 

 have constituted the primary objective of many 

 studies. On the other hand, many investigators ha\e 

 initiated cerebellar studies with the objective of 

 defining somatotopic relationships within the cere- 

 bellum. Luciani (18B-190) early emphasized the 

 conclusion that there was a lack of somatotopic 

 organization within the cerebellum with the excep- 

 tion of the relation of one side of the cerebellum with 

 the ipsilateral side of the body. Nevertheless, Bolk's 

 comparative anatomical studies (27), appearing at 

 about the same time that information concerning 

 the somatotopic organization of the cerebral motor 

 cortex was being re\ealed, gave great impetus to at- 

 tempts to demonstrate a similar organization of the 

 efferent functions of the cerebellum. Studies of the 

 more detailed anatomy of the cerebellum soon led 

 Edinger (116) and Comolli (77) to suggest another 

 variety of organization. According to this concept, 

 the paleocerebellum comprising the vermis and 

 flocculus was phylogenetically older and was con- 

 cerned primarily with the regulation of tonus; the 

 neocerebellum, on the other hand, consisting of the 

 cerebellar hemispheres, was primarily concerned 

 with cerebral relationships. Ingvar (164, 165) added 

 to this concept by proposing that the paleocerebellum 



