1. Specific precipitates resulting from the interaction of the homologous capsular polysaccharide and Type I antipneumococcus horse and rabbit sera have been analyzed by gasometric micro methods for total nitrogen, lipid nitrogen, and lipid carbon.
2. Lipid may, under certain conditions, form as much as 51 per cent or as little as 4 per cent by weight of specific precipitates.
3. The total lipid content of specific precipitates, within the range studied, is entirely independent of the protein content.
4. Lipid nitrogen forms a very small but detectable portion of the total nitrogen of precipitates.
5. The absolute lipid content of precipitates is a function of the concentration of lipid in the reacting mixture prior to precipitation, and seems to be governed by the laws of adsorption phenomena.