IN NATURE of May 27, p. 908, reference was made to the Dutch Congress of Natural Science and Medicine held at Nijmegen on April 11-13. A correspondent has sent the following notes on some of the medical papers. On the first day of this Congress the main medical paper was read before a very large audience by Prof. B. Brouwer, of Amsterdam. Prof. Brouwer spoke on the hydrodynamic intra-cranial and intra-vertebral conditions in connexion with the development of modern neuro-surgical diagnostic and operative technique. He showed very clearly the great importance which is attached to very simple physical examinations of the cerebral fluid and the ventricular system for the localization of ultra-cranial and intra-vertebral space-occupying lesions. Prof. Brouwer stressed the point that ventricular estimation and ventriculography—when in safe hands-are of the greatest value for the early diagnosis of many intra-cranial space-occupying lesions. Dr. A. Bie-mond, of Amsterdam, spoke on the diagnosis of mid-line brain-tumours. Going over a list of the ante-and post-mortem findings of twenty mid-brain tumour cases, Dr. Biemond tried to divide this material into three groups, according to their clinical picture and their operability. The prognosis, however, of mid-brain tumours, even in the light of modern neuro-surgery, is not very hopeful, according to Dr. Biemond's experience. Very much in contrast with this paper was the contribution of Dr. F. Verbeek, of Groningen. Dr. Verbeek described the tremendous advances which have been made during the last twenty years in the neuro-surgical field. A review of his neuro-surgical patients gave much more hope that even the mid-brain tumours will be accessible for operative treatment. Dr. A. Brouwer (Eindhoven) spoke on the technique of X-ray photography. Dr. C. E. Burger (Eindhoven) dealt with X-ray photography as a method for mass examination in the attack on tubercular infection. Dr. J. H. van der Tuuk (Eindhoven) spoke on deep X-ray treatment and its measurement, with reference to apparatus operating up to one million volts.