Many students of the coronary circulation must have noted that the ventricular zone affected by ligating a large coronary branch not only appears cyanotic and dilated, but that it seems to alter in its mode of contraction. The detailed and sequential changes in contraction are not easily followed by the unaided eye and so far have not been recorded myographically. The reasons for this were the lack of an adequate and suitable myograph and a technic for the application of one to a limited ventricular surface so that records obtained represent, at least reasonably well, changes in muscle length and not predominantly artefacts due to position changes, thrusts and vibrations of the vigorously beating ventricle. This communication concerns itself with descriptions of a technique and of a type of optical myograph suitable for such studies and an analysis of the changes in optical myograms which follow clamping of a large coronary vessel. 1 The expenses of this investigation were defrayed partly from a grant to one of us (C. J. W.

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The clinical course and histologic findings are presented of an infant with an unusual form of pulmonary dysplasia. Characteristic sonographic findings and progressive hypoxemia led to the diagnosis of persistence of the fetal circulation. The patient expired despite ventilatory and pharmacologic intervention. Postmortem findings of severe pulmonary capillary hypoplasia, despite normal anatomical and biochemical parenchymal maturation, were observed. It is suggested that factors controlling pulmonary capillary maturation may be significantly different from those involved in airway and pulmonary parenchymal development.

In a previous paper (1) the marked biological effects of neutrons on mammalian tissue were demonstrated, as evidenced by the production of a lymphopenia in white rats after whole body irradiation. As is true after x-rays, the lymphocytes were more sensitive to neutrons than were the other blood cells. In a further study (2), it was found that neutrons were effective in vitro on Sarcoma 180, a transplantable neoplasm of white mice. At that time also, the whole bodies of mice were exposed to various doses of x-rays and neutrons, and the lethal effect of neutrons was demonstrated. The preliminary observations indicated that the mechanism of death after irradiation with neutrons was similar to that after x-radiation.It is important that we understand the effects of whole body irradiation with neutrons for two reasons. First, throughout the world, there are at present numerous laboratories using this new form of radiation in studies in the field of nuclear physics. The workers in these laboratories are exposed in a greater or less degree to neutrons, concerning whose biological effects we know little. The early and late damaging effects suffered by the early workers with x-rays force us to consider the possibility of similar serious injury from exposure to neutrons. Secondly, the biological action of neutrons on mammalian normal and neoplastic tissue, suggests their trial in the treatment of