1. The particle diameter of bluetongue virus (sheep virulent and egg
adapted virus) was determined by gradocol membrane filtration.
2. Details of the technique for clarifying infective emulsions by aluminium hydroxide adsorption and trypsin digestion are given.
3. The density of the egg adapted virus was calculated from data
obtained from centrifugation in media of low and high specific gravity and was found to be 1.147.gm./cm.³ in strong cane sugar and 1.106 gm/cm.³ in serum albumin.
4. The particle diameter of the sheep virulent virus was determined
approximately, and of the egg adapted virus accurately by centrifugation.