In a series of five cases of spastic paraplegia in which lumbar sympathetic neurectomy was performed for the relief of muscular spasticity, blood flow and skin temperature determinations, before and after operation, were carried out. Calorimetric studies were made with the Stewart-Kegerreis foot calorimeter to determine the heat production and radiation of the lower extremities. Surface temperature estimations and intensive clinical studies showed conclusively that marked vasodilatation took place immediately after removal of the second, third and fourth lumbar ganglions and sympathetic cord, and after severing of the gray rami. The lower extremities became hot and dry. The skin temperature in the feet increased from 2 to 7 degrees following operation. Increase in the heat production and dadiation of the feet from 200 to 900 per cent, was likewise noted (Chart 1). There were mild color changes in the lateral aspects of the feet. The skin exfoliated, and sweat gland