CEREBELLUM, PONS, AND MEDULLA. 235 



for the muscle sense or, expressed more generally, for the afferent 

 paths from the muscles. This view is connected usually with the 

 name of Lussana,* but has been supported since in one sense or 

 another by many observers.! It is, in fact, not essentially different 

 perhaps from the second phase of the first group of theories. Those 

 who have expressed their idea of the physiology of fhe cerebellum 

 by saying that it is a center of the muscle sense have, in recent 

 times at least, recognized that this sense has a cortical center also in 

 the cerebrum. The view can not assume, therefore, a conscious 

 muscle sense mediated by the cerebellum, but only that fibers of 

 deep sensibility have a cortical termination therein, and that 

 the cerebellar activity thus aroused is in some way necessary to 

 the orderly adjustment of complex voluntary movements. Some 

 authors have assumed that the reflex effect thus exerted on the mus- 

 culature of the limbs and trunk is not concerned directly in elaborat- 

 ing the proper co-ordination of the muscles, but consists essentially 

 in the production of a state of tonus of a variable or adaptive char- 

 acter, which serves as a foundation, so to speak, for the volun- 

 tary control of the muscles. It would seem to be evident that on 

 any theory of this kind the results of cerebellar activity must be 

 exerted through some efferent channel upon the muscles concerned 

 in equilibrium and body-movements. No direct efferent path be- 

 tween the cerebellar cortex and the motor centers of the cord has 

 been established satisfactorily, but it may be that the indirect path 

 through the superior peduncles to the red nucleus and thence to the 

 cord through the rubrospinal tract subserves this function. Accord- 

 ing to another point of view, the cerebellum is a great augmenting 

 organ for the neuromuscular system. It is added on, as it were, to 

 the cerebrospinal motor system, and serves not to co-ordinate the 

 motor discharges, but to increase their strength or effectiveness. 

 This general view, first proposed by Weir ■NTiU'hpll (ISOO), has been 

 supported by Luys, and especially, although with important 

 modifications, by Luciani. | Some of the details of the work of 

 the latter observer are given below. 



Experimental "Work Upon the Cerebellum. — Rolando, and par- 

 ticularly riourens, gave the dn-ection to modern experimentation 

 m this subject. The latter observer made numerous observations, 

 especially on pigeons, in regard to the effect of removing all or a 

 part of the cerebellum. He describes in detail the stril^ing results 

 of such an operation. When all or a large part of the organ is re- 



* Lussana. See "Journal de la physiol. de I'homme," 5, 418, 1862. 



t See Lewandowsky, "Archiv f. Physiologie," 1903, 129. 



t For the literature of the cerebelkim, see Luciani, "II cervelleto," Flor- 

 ence, 1891; German translation, "Das Kleinhirn," 1893. Also Luciani, article 

 "Das Kleinhirn," in "Ergebnesse der Physiologie," vol. iii, part ii, p. 259, 

 1904, and van Rynberk, ibid., 653, 1908. 



