An extensive neuropathologic study was undertaken on a young man aged 17\m=3/4\, who died in one of an extended series of attacks of hyperthermia. He had been studied rather exhaustively clinically, having been examined by more than one hundred physicians ; it was recognized during the latter part of his life that the attacks from which he suffered were most likely due to disturbed hypothalamic function.Since the study appeared to cast some light on thalamic and hypothalamic function, and more on hypothalamic regulation, it was deemed advisable to record the neurohistologic findings in some detail. The clinical data and the physiologic and psychosomatic aspects were discussed in the foregoing article.1 PATHOLOGIC REPORT Postmortem Examination.\p=m-\Theexamination was performed two hours after death. The body was that of a small, somewhat poorly nourished white male whose size and conformation suggested an age not over 12 or 14 years. The hair was sparse except on the head and was normally distributed.The genitalia were immature: the testes and epididymides were distinctly smaller than normal. The pros¬ tate gland was infantile in size and wras compressed and scarcely recognizable. The adrenal glands were some¬ what smaller than average. The thymus was distinctly large, measuring 10 cm. in length and varying in width from 1 to 3 cm. and in thickness from 0.5 to 1.5 cm. The spleen was moderately enlarged.All extremities were of proportionate size and develop¬ ment. There were some clubbing of the finger tips and reddening of the distal phalanges. The muscular tissue everywhere appeared grossly diminished ,in amount; there was no. focal muscular atrophy.Microscopic Examination of the Viscera.-Exclusive of changes in the nervous system, the micropathologic findings consisted of a moderate degree of focal acute pneumonitis, chiefly peribronchial in distribution. There was marked thickening of the bronchial walls due to