It may be stated as favourable to this view of the mental nature of the power by which vo luntary movements are coordinated, that, in the first moments of life, provision is made for the perfect performance of all those acts which are of the physical kind. Thus, respiration and deglutition are as perfect in the new-born infant as in the full-grown man ; and the exci tability of the nervous centres to physical im pressions is much greater at the early age, partly perhaps in consequence of the little interference which is received at that period from the will.
That the cerebellum is an organ favourably disposed for regulating and coordinating all the voluntary movements of the frame is very apparent from anatomical facts. No other part of the encephalon has such extensive connections with the cerebro-spinal axis. It is connected slightly indeed with the hemispheres of the brain, by the processus cerebelli ad testes, but most extensively with the mesoce phale, the medulla oblongata, and the spinal cord. Now it is not unworthy of notice that its connection with the brain proper is more immediately with that part, which may be re garded as the centre of sensation; namely, with the optic thalami. This connection of the cerebellum with the centre of sensation may probably have for its object to bring the mus cular sense to bear upon the coordination of movements, in which the individual experience of every one shows that that sense must mate rially assist.
The cerebellum is brought into union with each segment of the great nervous centre upon which all the movements and sensations of the body depend; through the restiform bodies it is connected with the medulla oblongata and the spinal cord ; by the fibres of the ports with the mesocephale, and thus with tile ante rior pyramids and corpora striata; and through the processus e cerebello ad testes with the optic thalami. What can be the object of these extensive connections ? It would be difficult to conceive any function for which so elaborate a provision would be more necessary, than that of regulating and coordinating the infinitely complex movements which the mus cular system is capable of effecting ; more especially when it seems highly probable that the antero-lateral columns of the cord, and the antetior pyramids and olivary columns supply all the anatomical conditions necessary for the developement of acts of sensation and volition.
It thus appears that Flourens' views re specting the office of the cerebellum derive considemble support both from experiment and from anatomy. When we come to collect the evidence on this subject which has been fur nished by the effects of disease, we obtain very little information of a satisfactory kind. A
superficial lesion of either cerebellar hemi sphere or of the median lobe does not cause paralysis, but may produce delirium or con vulsions, as a superficial lesion of either ce rebral hemisphere may; but a deep-seated lesion of the cerebellum involving the central white substance which is continued from the crus cerebelli causes hemiplegia on the oppo site side. This similarity between the effects of cerebellar and of cerebral disease is a re markable and highly interesting fact, but one which considerably increases the difficulty of obtaining from pathological phenomena any contribution to the solution of physiological questions. It may be explained thus:—the transverse fibres of the pons passing, through the mesocephale would propagate to this segment the morbid influence of any deep-seated lesion of the cerebellum, and thus affect the adjacent pyramid, which again would affect the opposite half of the body just as if the morbid influence originated in the cerebral hemisphere. It is, then, this secondary affection of either pyra midal body which obscures the proper signs referable to cerebellar lesion.
A few cases, however, have been put on re cord, in which a tottering gait, like that of a drunken man, and a defective power of co ordination existed in connection with a diseased state of cerebellum. A striking instance of this occurred under my own observation : a young surgeon, who had recently received an appointment in the medical service of the army, was in attendance in the military hos pitals at Chatham, preparatory to his nomina tion to a regiment. It was observed that as he walked he staggered to so great a degree that he was suspected of dtinking to excess, and was put under arrest on this account. It was soon, however, found that lie was suffer ing under symptoms of diseased brain, and he was sent up to town and placed under my care. I found that his principal symptom was extreme difficulty in the coordination of his movements, accompanied by a sense of gid diness in the head. Ile could neither stand nor walk, yet there was no distinct paralysis, for while he was in the recumbent posture he could move about his limbs freely. After a time he became amaurotic and comatose. The post-mortem examination revealed softening of the left crus cerebri and a patch of yellow soft ening on the corresponding restiform body : there was in addition a recent deposit of lymph at the base of the bmin around the optic com missure.