Although, as will be subsequently pointed out, philosophical speculation on cerebral physiological problems long preceded the work on the finer anatomy of the cerebral cortex, the latter study, in turn, has preceded the more refined physiological investigations with which it has been associated during science's dizzy dash of the past six decades. It will be shown that a fairly well defined concept of cellular formation had already been evolved by 1870 when the centuries-old gestation period of neuro-physiology ended. Because of this real precedence, the cytoarchitectonic study in its narrow sense will be the first to be presented. Associated with this will be a glimpse at the embryology of the cortical layers, introduced to round out the survey. The valuable work of past investigators in myelo-architectonics has not been treated because it lacks the potentialities found in cytoarchitectonic studies. The phylogenetic aspect, though interesting, seems too far afield for a work of the magnitude of this presentation.

The belief that it is necessary to fill every dural defect with some type of membrane has been the basis of much of the experimental work on dural deficiency as well as the surgical treatment of dural defects. On the other hand, there is the opinion, based on clinical experience and some experimental studies, that the dura takes good care of its own defects.

Audiology in general, and audiometric techniques in particular, have made commendable progress in the last few decades. The threshold for pure tones and speech can be accurately established and at subsequent examinations can be confirmed or compared, with a fair amount of precision. The articulation score for phonetically balanced words can be determined and so can the effect of amplification on such scores. The conductive and the cochlear component of hearing loss can be distinguished with a fair amount of reliability from what is called the "sensorineural" or the "retrocochlear component".

Quick frozen section of brain tumors, as well as the smear technique developed here at the Montreal Neurological Institute by the late Dr. W.V. Cone are extremely valuable means for arriving at a preliminary pathological diagnosis which can be relayed to the surgeon prior to the completion of an operation. We felt, however, that the fine histological distinction between benign and malignant intracranial lesions which arises in some cases could not be readily resolved by using the above techniques alone and that, perhaps, a technique could be devised to help clarify these problem cases.

Since Caton (1875) recorded electrical potential change from the exposed brain of a rabbit and, later, Berger (1929) demonstrated electrical currents produced by the living brain of man, the study of electrical activity of the cerebral cortex has become increasingly important in the understanding of brain function. However, the analysis of this activity is not an easy task, not only because of the extreme complexity of the structure of the cerebral cortex, but also because of the inadequacy of the methods conventionally used for the recording of the cortical activity.

The object of this work is to provide a morphological guide for the conduct and analysis of experiments carried out on the brain stem of the cat. In particular, the work contains a series of photomicrographic illustrations of the cat brain stem upon which are delineated the major nuclei as distinguished by the classical cytoarchitectural criteria and a set of stereotaxic coordinates referrable to modern adaptations of the Horsley-Clarke stereotaxic instrument.

Rasmussen, T.This study was conducted during the years 1960-61 when I was appointed a Hosmer Teaching Fellow in the Department of Otolaryngology, McGill University, at the Royal Victoria Hospital, Montreal. The original plan of this study was to evaluate the possible effect of some temporal lobe lesions upon vestibular function. It has been reported that a lesion of the temporal lobe may produce directional preponderance of nystagmus to the side of the lesion in response to calorie stimulation. (Fitzgerald and Hallpike 1942, and Carmichael, et al, 1954).

The mechanism of headache has been studied physiologically by the neurosurgeon, whose conclusions have sometimes proved difficult to correlate with known anatomical facts. This is because of the relative paucity of knowledge concerning intracranial sensory nerves and nerve endings so that the interpretation of physiological investigations has depended to some extent on speculation. There are at present two main groups, one which would consider the pain of headache as mediated solely or almost entirely by periarterial nerves and receptors, the other which attributes to nerves within certain special locations of dura the chief role in pain conduction. The present study has approached the problem from two aspects, the first anatomical, special interest being taken in nerve endings in dura, the second clinical, observations on dural sensitivity in man. It has become apparent that both dural vessels and sinuses as well as certain cerebral vessels are pain - sensitive, but in addition that parts of dura itself are sensitive. Furthermore complicated corpuscular nerve endings demonstrated in dura suggest that afferents other than pain fibres leave the dura. These may play a part in reflexes which control vasomotor tone or even play a part in the regulation of intracranial pressure.

Despite the advances of electrophysiology and the passage of fifty years, the conclusions of John Hughlings Jackson as regards the mechanisms involved in idiopathic epilepsy are today not only being confirmed, but are serving as a basis for farther investigation. Studies of cortical localisation of onset in various forms of epilepsy have failed to reveal a focus of onset for petit mal attacks. Major generalised convulsive seizures ("grand mal") of bilateral onset have also defied attempts at localisation at the level of the cortex.

This investigation was carried out at the instigation of Dr. W. V. Cone in the attempt to discover chronic pathological changes in oligodendroglia. Knowledge of chronic changes in the oligodendrocytes has not been greatly advanced m the past twenty years. At that time it was stated that: "Unlike astrocytes, the disappearance of myelin does not result in an increase but a decrease of the oligodendrocytes and it is quite possible that with myelin degeneration oligodendrocytes are transformed into astrocytes." (Penfield 1932).