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When the basal ganglia are damaged by disease processes in man, various disorders of movement occur. In order to control movement the basal ganglia must have a sensory input and in the absence of direct connections to motoneurones or motor cortex they must act through intermediate structures. The experiments, on cats, demonstrate: (1) which sensory inputs reach the caudate nucleus and how they influence activity of the neurones there; (2) the effect of the output from the caudate nucleus and globus pallidus on the neurones of the inferior olive and reticular formation. The results are discussed with respect to the control of movement.

The distribution of HVA in various regions of the grey and white matter of the human brain has been examined. HVA was found to occur in appreciable amounts in the following regions: (a) Grey matter - putamen, caudate nucleus, globus pallidus, substantia nigra, red nucleus, subthalamic nucleus, thalamus, lamina quadrigemina; (b) White matter - all components of the internal capsule (anterior limb, genu, posterior limb, supralenticular part), pes pedunculi, white matter of the cortex. From the characteristics distribution pattern of HVA within the internal capsule (lowest concentrations in the caudal parts of the posterior limb, highest values in the anterior limb), and from the results obtained in parkinsonian brains, it is concluded that dopamine-containing fibres are present in the internal capsule running in rostral direction to reach the striatum. These dopamine fibres are assumed to originate in the substantia nigra. Contrary to this, the biochemical source and significance of the HVA found in other brain regions than the striatum, the substantia nigra and the internal capsule (i.e. globus pallidus, red and subthalamic nuclei, thalamus, lamina quadrigemina, and possibly also pes pedunculi and white matter of the cortex) remain unexplained as yet.

In the following paper a case ofétat dysmyéliniséof the globus pallidus, or as it is often synonymously called,“Hallervorden-Spatz disease”, will be presented. Records of thoroughly studied cases of this condition are still rather scanty and there is much need for a systematic extension of experience, the more so since, as Helfand (16, 17) has recently pointed out, progress in the elucidation of the condition has not always been enhanced by generalizations from findings based on too small a case-material. We are happy in having at our disposal the vast resources of the London County Mental Hospitals. It is hoped to follow up this paper by publishing further cases of a rather different nature, though with some characteristics in common with the case described here.

The terms rigidity and spasticity are considered to denote different states in clinical neurology. Liddell and Sherrington9pointed out that the stretch reflex in decerebrate cats consisted of 2 phases, one being the "phasic" component, which appeared only during the period of increasing muscle stretch, and the other the "tonic" or "postural" component, which existed during the continuously sustained stretch. In previous papers, we11,12have reported that these 2 components can be demonstrated in the so-called hypertonic states of "extrapyramidal" disease and that the tonic component is more markedly and selectively decreased by stereotaxic pallidotomy than the phasic one. This paper is an investigation of the neurophysiological mechanisms which underlie these 2 patterns of stretch reflex, with particular reference to their relationship to the globus pallidus. The concept of a gamma loop, proposed by Granit,3introduced a plausible physiological explanation of the rigid and spastic states. The

p ARKINSONISM is a well-documented syndrome and its pathology has been widely studied. The current surgical treatment of this disorder is carried out by focal interruption of nerve pathways in the region of the thalamus and basal ganglia. In the Department of Surgical Neurology, Edinburgh, the stereotax~.c method employed is that described in 1958 by Guiot 2 and modified in 1960 by Gillingham. 1 A posterior approach is used, and thalamic, capsular, or pallidal lesions can be achieved through one track (Fig. 1 ). A thermal lesion is made by electrocoagulation at the planned target areas, which are usually in the ventrolateral nucleus of the thalamus in the midcommissural plane, 5 mm above the intercommissural plane and 12 to 17 mm from the midsagittal plane, and in the medial segment of the globus pallidus 3 mm behind the anterior commissure, 1 mm below the intercommissural plane and 12 to 17 mm from the midsagittal plane. A stainless steel ball is inserted at the target point after coagulation (Fig. 2) , and its position can be charted on the stereotaxic atlas of Schaltenbrand and Bailey. 3 The purpose of this paper is to compare the planned positions of the surgical lesions with their actual positions as determined by postmortem examination.

Though many of the earlier workers made statements based on general impressions from injected preparations about the relative vascularity of different parts of the brain, only comparatively recently has an attempt been made to measure and express numerically the capillary development in different areas, by methods similar to those used by Krogh in studying the vascularity of muscle. Craigie has made an extensive study of the rat brain by such methods, Cobb, and Cobb and Talbot have investigated certain areas of the rabbit brain, and Dunning and Wolf certain parts of the nervous system of the cat. In the present paper a personal investigation (undertaken at the suggestion of Dr. Cobb) is reported, comparing the basal ganglia, cerebral and cerebellar cortex of the cat as regards capillary vascularity. The capillaries were demonstrated by Indian ink injection, and results expressed in millimeters of capillary per cubic millimeter of tissue. Substantiating observations were made on similar areas of monkey and human brains, but without attempting accurate measurement as in the cat material. The results indicate a striking variation in vascularity in the various areas of grey matter examined; the globus pallidus was found to be by far the least vascular area; the basal ganglia were on the whole less vascular than cerebral neocortex or cerebellar cortex, though the lateral geniculate body had as high a vascularity. To a certain extent Craigie's statement that the receptive and associative areas have a higher vascularity than the efferent areas was confirmed. Furthermore, a correlation could be made between the vascularity and the richness in ganglion cells of the various areas; there were, however, striking exceptions to this correlation—for instance, the granular layer of the cerebellum has a relatively low vascularity in view of its extremely dense cellularity. This, like Dunning and Wolf's demonstration of the relatively low vascularity of the cat's trigeminal ganglion, suggests that the metabolic activity of an area of nervous tissue (as measured by its vascularity) is not necessarily in proportion to its richness in ganglion cell bodies. The relationship, if any, of richness or poverty of capillary development to the selective localization of anoxaemic lesions remains obscure. That selective necrosis in carbon monoxide poisoning occurs in the globus pallidus, the least vascular area of grey matter so far examined, is superficially suggestive; but while the vascularity of this area is poor, so also may be its oxygen need for survival (as is suggested by its sparseness in ganglion cells), and there is no means of knowing as yet whether this or any other area has a low margin between anatomically available capillary bed and oxygen need.

In about six years' use of the stereotactic operation in this laboratory, during which the first, second, and third models of the stereoencephalotome were completed, our main concern has been the globus pallidus and the thalamus. Several reports have previously been published on the technique used and the earlier results. In this paper, the treatment of rigidity and tremor of Parkinsonism, using a stereotactic injection of procaine HCl in oil and wax, will be described and discussed. We believe that stereoencephalotomy, in addition to the opportunities for treatment that it offers, provides an approach to an investigation of the function of the subcortical ganglia. Since James Parkinson described paralysis agitans (Parkinson's disease) as a senile disorder in 1817, the neuropathology of this disease has been studied by many investigators. At first this disease was thought of as a senile process for which a hereditary predisposition was assumed. But after the

The parkinsonian syndrome following epidemic encephalitis has terminated fatally with sufficient frequency to permit numerous, though scattered, observations on the pathologic picture. The following brief review of the available literature will serve to indicate the differences of opinion which exist, relative particularly to the role of the globus pallidus or substantia nigra lesions in the production of the syndrome. Lesions in the substantia nigra have been admitted by proponents of the idea that globus pallidus involvement is the essential feature of the pathogenesis of the disease and, conversely, globus pallidus lesions have been described by most of the observers who would place the seat of the difficulty in the substantia nigra. Up to the present no one has undertaken a detailed evaluation of the quantitative amount of cell destruction in these regions in any case. The purpose of this paper is to present the findings of such a study in