The first lecture dealt with the general composition of nervous structures. Grey matter contains 80—90 per cent. of water, and 50 per cent. of the total solids are proteid. In white matter there is less water and less proteid, and in peripheral nerves is least water and least proteid. The most abundant proteid is a nucleo-proteid containing ·5 per cent. of phosphorus, but there is little of this in the white matter. The other two proteids are globulins, one of which coagulates at 47° C.