As a result of two operations which were performed on a rhesus monkey with the object of working out an approach for the destruction of the anterior nuclei of the thalamus, not only were the latter involved, but lesions were also produced in the frontal lobe. The lesions were largely caused by the removal of firm adhesions which had developed after the first operation. The motor disturbances and the mental changes which appeared after the second operation revealed some features which had much in common with a clinical syndrome previously observed in a patient who had died from a frontal lobe tumour in the same region. For this reason it seems worth while to record and to discuss these two cases. The experimental operations may be described in some detail in order to explain the extent of the lesions produced.

During the course of the last few years the study of the cerebrospinal fluid in both mental and nervous disorders has made rapid progress, and with the introduction of methods of precision much useful knowledge in regard to its physical, chemical, and serological properties has been acquired. Nevertheless, much remains to be learnt, and we propose to submit observations on one aspect of the subject which is still in its infancy, namely, the pressure of the cerebrospinal fluid, and the modifications which it may undergo in the insane. At the outset, however, it will be convenient to refer in as few words as possible to the distribution and circulation of this fluid.

Within the last year a series of papers has been issued (1, 2, 3) from this laboratory indicating that in the psychotic there exists a disturbed regulation of the respiratory mechanism for the control of acid-base equilibrium, which, in the cases examined, mainly depressed psychoses, manifested itself as an inexcitability of the respiratory centre, shown by a failure of response to CO2 stimulation. The work was done on uncertified borderline cases of insanity; it has since been confirmed by Marsh (4) on certified patients, and his results in 73 cases confirm the original findings and indicate plainly that dementia præcox and depressive psychoses fall into a group showing a variable inexcitability of the respiratory centre. The question naturally arises whether this condition is a cause or an effect of the mental state, and, from the point of view of cause, whether it is due to the drug-like action of some substance arising from faulty metabolism, or is an exhaustion effect. The question of intestinal toxæmia obviously needs investigation in this respect. This subject has been freely discussed in the literature and its significance becomes of greater importance in relation to psychoses owing to the work of Buscaino (5, 6) and Scheiner (7, 8) in Italy, and of Stewart (9) in this country. Buscaino describes a reaction of the urine with silver nitrate in certain psychotic cases, alcoholic insanities and dementia præcox, and from this assumes the existence of a toxic substance from liver derangement in these cases. He further describes lesions of the small intestine of mental patients which may result in undue permeability of its walls; it is not proposed to discuss this latter aspect of his work, but to deal with his silver nitrate reaction.