THE SPECIAL NERVOUS MECHANISMS 125 



and direct connections with almost all kinds of receptors. But 

 such injuries or operative interference do produce serious motor 

 disturbances, so that ordinary, automatic, or customary move- 

 ments, such as those of gait, locomotion, and posture, are greatly 

 affected, and the animal when walking, running, swimming, or 

 flying, behaves in an ineffective, incompetent manner. "What- 

 ever, then, are the functions of the cerebellum, it is very plain 

 that they must be of considerable importance and are very 

 complex — a deduction from the peculiar and most intricate 

 structure of the grey matter of this organ. The general con- 

 clusion attained by the study of all these lines of evidence is that 

 the work of co-ordination of movements performed customarily 

 and automatically is carried out in the cerebellum. Impulses 

 arising in the sense receptors are conveyed to their nuclei in 

 the spinal cord and brain, or they may be conveyed directly 

 into the cerebellum, and if the direct path does not exist, there 

 is one connecting the immediate nucleus of the afferent impulses 

 with the latter part of the brain. That is to say, the cerebellum 

 is the recipient of impulses coming from the receptor organs, 

 and particularly from those which have to do with equilibration 

 and those others which come from the acting muscles themselves 

 and from the joints (where the efiort involved in the movements 

 of the limbs must be particularly felt). On the other hand, the 

 cerebellum also stands in close connection with the nuclei which 

 give origin to impulses going out to the muscles of the limbs and 

 body. There is, therefore, a mechanism whereby those complex 

 movements which are the means of locomotion may be timed, 

 adjusted, and co-ordinated, and this we suppose to be situated 

 in the grey matter of the cerebellum. Of the nature of the 

 mechanism we have not even a suggestion. 



Cortical Control. 



We shall consider in the next chapter the experimental 

 evidence on which our knowledge of the functions of the cortex 

 cerebri is based, and in the meantime we deal only with the 

 nervous mechanisms themselves, so far as these have become 

 known by anatomical research and experiment. The greater 

 part of each cerebral hemisphere, then, is a core of nerve fibres 

 making such connections as are indicated in Figs. 28 and 29 — 

 connections, that is, between the various parts of the cortex 

 itself and between it and the other nuclei in the lower brain, 

 cerebellum, and spinal cord. With the exception of the corpora 



