and the cerebral hemisphere of the opposite side, and what is its probable nature. 5. Whether one lateral half of the cerebellum is related mainly to the same side of the spinal cord, to the opposite side, or to both, and what the nature of the relationship is. 6. What symptoms resulting from experimental lesions of the cerebellum are mostly to be relied on for localisation. 7. Whether any, and if so which, of the symptoms are dependent on interference with the labyrinth or 8th nerve when experimental lesions of the cerebellum are produced. The procedures adopted in attempting to elucidate these problems were: 1. Median vertical section separating the two lateral halves of the cerebellum from each other. 2. Extirpation of one lateral lobe. 3. Removal of half the organ, i.e., of one lateral lobe together with one lateral half of the middle lobe. 4. One or other of the last two methods of procedure as a preliminary, and subsequent comparative investigation of the excitability of the two cerebral hemispheres. 5. Similar preliminary methods as in the last instance, followed by the administration of the essential oil of absinthe, and comparison of the effect of the resulting convulsions on the muscles of the two sides of the body. 6. Removal of both lateral lobes of the cerebellum. 7. Extirpation of the whole or half of the posterior part of the middle lobe. 8. Ablation of the whole organ. 9. Control experiments on the labyrinth and 8th nerve, which consisted in: (a) Extirpation of the labyrinth. (b) Intracranial section of the auditory nerve. (c) Chemical irritation of the auditory nerve. The results detailed refer chiefly to dogs, but the effects of similar lesions of the cerebellum in monkeys are contrasted with these. The question as to whether the cerebellum exerts any trophic influence is separately considered, as is a case of defective development of the cerebellum in a cat. The investigation of the excitability of the two cerebral hemispheres, as tested by the induced current, yielded results of more than ordinary interest, for, whereas the excitability was equal on the two sides when the cerebellum was intact, the opposite hemisphere was the most excitable after unilateral ablation of the cerebellum, which difference in the excitability persisted, and was still present even three months after the half of the cerebellum had been removed. The results obtained when absinthe was administered to animals which had been deprived of half the cerebellum also yielded highly interesting and instructive results. The increased excitability of the opposite hemisphere was evidenced by the exaggeration of the convulsions on the side of the cerebellar lesion; and it became also evident that the convulsions on the opposite side were diminished. Further, the curves obtained from the extensor muscles of the anterior extremity on the side of the cerebellar lesion showed that there was a marked alteration in the second stage of the convulsive seizure, for the tonus characteristic of this stage of similar convulsions evoked in dogs whose central nervous system was intact was either replaced by clonic spasms, or a large element of clonus was superimposed on the tonus. The curves from the muscles of both anterior extremities showed this alteration in the second stage of the convulsions when the whole instead of the half of the cerebellum had been previously removed. The one The chief conclusions which appear to be warranted are that the one half of the cerebellum does not, in any great measure, depend on the cooperation of the other half for the proper performance of its functions. The bulk of the impulses pass from one half of the organ to the cerebrum, or spinal cord, without passing to the other half. Three factors are responsible for the defective movements which result on ablation of different parts of the organ-incoordination, rigidity, and motor paresis. The last of these is probably directly due to the withdrawal of the cerebellar influence from the muscles, while the exalted excitability of the opposite cortex cerebri, which results after unilateral ablation of the cerebellum, is probably a provision for compensation in this and other connexions. half of the cerebellum controls the cells of the cortex of the opposite cerebral hemisphere, and those of the anterior horns of the spinal cord on the same side chiefly, and on the opposite side to a slight extent. It is further suggested that either the cerebral hemisphere whose excitability is increased inhibits the opposite hemisphere, or that, under normal conditions, one half of the cerebellum inhibits the other half, which inhibition being no longer operative, owing to ablation of half of the organ, allows the remaining half to exert an increased control on the opposite cortex cerebri, or on the spinal centres of the same side, or possibly in both directions; but which is the most probable explanation of the phenomena observed is at present left an open question. The symptoms characteristic of unilateral ablation of the cerebellum are: 1. Rotation and reeling to the opposite side. 2. The side of the face corresponding to the side of the lesion is directed up, and the spinal column is arched with its concavity to the side of the lesion. 3. Incoordination, chiefly in the limbs of the same side. 4. Rigidity, most marked in the extremities of the side of the lesion, and preponderating in the anterior extremity of the side. 5. Exaggeration of the tendon reflexes most marked on the same side. 6. Motor paresis affecting both extremities on the side of the lesion, and the posterior extremity of the opposite side. 7. Anæsthesia and analgesia having the same distribution as the motor paresis. 8. Deviation of the opposite eyeball downwards and outwards, while that of the same side, if deviated, looks upwards and to the side of the lesion. 9. Lateral nystagmus, the jerks being from the opposite side towards the side of the lesion. The phenomena which characterise ablation of different parts of the middle lobe, and of the whole organ, are similarly described. Incoordination is next discussed, and it is urged that, instead of looking on the cerebellum as a distinct organ which has a special function, distinct from those subserved by other parts of the central nervous system, it would be more correct to look on it as a part of that system, having many functions in common with other parts of it, the chief difference between one part of this great system and another being the degree in which different functions are represented in any given part: e.g., with regard to motor power, the anterior extremity is maximally represented in the cerebrum and minimally in the cerebellum, whereas the trunk muscles are minimally represented in the cerebrum and maximally in the cerebellum. Arguments are adduced in favour of looking on the ocular deviations which result from ablation of parts of the cerebellum as paralytic rather than irritative phenomena, and two forms of nystagmus are recognised as consequent on cerebellar lesions, one which is spontaneous, and the other which is only evoked on voluntary movements of the globes, and the probable difference in their aetiology discussed. Finally, the phenomena characteristic of unilateral ablation of the cerebellum are contrasted with those the result of extirpation of the labyrinth, and it is shown that no single phenomenon is the same in the two. III. "The Effect produced upon Respiration by Faradic Excitation of the Cerebrum in the Monkey, Dog, Cat, and Rabbit." By W. G. SPENCER, M.S., M.B., Assistant Surgeon to the Westminster Hospital. Communicated by Professor VICTOR HORSLEY, F.R.S. Received December 15, 1893. (From the Pathological Laboratory of University College, London.)* (Abstract.) The author of the paper brings forward evidence to show that, whilst the effect upon respiration of exciting the cerebrum in a non-anaesthetised animal is probably a complex one, yet, by careful regulation of the anesthetic state, four constant effects can be obtained upon respiration by stimulation of the cortex, and these can be traced down each in a course of its own from the cortex to the medulla oblongata. In the production of the anesthetic state the author lays stress not only upon the drug (ether) used, but also upou the following general conditions-apnoea, loss of blood, exposure of the brain, extravasation of blood, general exhaustion of the animal, and departure from health prior to the experiment. The four effects upon respiration obtained in this research are as follows: : A. Diminution of Action. Slowing and Arrest of the Respiratory Rhythm.-The cortical area where this result was obtained is situated just outside the olfactory tract in front of the point where the tract joins the temporosphenoidal lobe. On exposing successive and vertical sectional surfaces of the hemisphere the same result was obtained by exciting in the line of the strand of fibres known as the olfactory limb of the anterior commissure. After decussating at the anterior commissure, the tract is continued backwards on either side of the infundibulum into the red nucleus below and external to the aqueduct at the plane of exit of the 3rd nerve. B. Increased Action. 1. Acceleration.-Commencing from a point on the convex surface of the cortex within the "sensori-motor area, the effect may be followed back just below the lenticular nucleus where it borders on the outer and ventral portion of the internal capsule; the strand runs Grants have been made towards the research by the Royal Society and by the British Medical Association, at first external and then ventral to the motor portion of the internal capsule, and so reaches the tegmentum. The lines from the two sides meet in the interpeduncular grey matter at the level of and just behind the exit of the 3rd nerve. 2. Hyperinspiratory Clonus ("snuffing movements").-This effect was obtained by excitation at the junction of the olfactory bulb and tract, and then carrying the stimulation backwards along the olfactory tract; the same result was found when the uncinate convolution of the temporo-sphenoidal lobe was irritated. Followed from the uncus this excitable region passed behind the optic tract to the crus, and then lay ventrally to the crusta. The excitable tract on each side thus converged towards the middle line at the upper border of the pons. 3. Hyperinspiratory Tonus.-This experimental result is of such frequency and constancy as to be clearly an important general phenomenon. It can be elicited in various ways: e.g., excitation of the descending motor tract in the corona radiata and internal capsule yielded this result; so did excitation of the 5th nerve and dura mater, as well as the sciatic nerve, both before and after complete removal of the cerebrum at the tentorium cerebelli. The author finds medullated fibres in prepared microscopical vertical (frontal) sections of the brain running in the same course as that indicated by faradic excitation of the living surface of the section of the hemisphere. For his conclusions he has relied solely upon tracings of the respiratory movements. Fifty-six tracings are included as illustrations, together with thirty photographs of brains and brain sections to show the precise points excited. The author records his thanks to Mr. Horsley for help, and to Dr. Howard Tooth for the loan of excellently-prepared sections. IV. "The Pathology of the Edema which accompanies Passive (From the Pathological Laboratory, Cambridge.) The author reviews the literature of the subject, and points out that the question of time has not been sufficiently considered by previous investigators. He examines the view which, at present, is usually accepted, and which explains the oedema accompanying passive congestion upon purely mechanical principles. |