From tissues it is obtained by extracting with warm alcohol and ether, concentrating the extract, precipitating with acetone and repeating the operations. Pure lecithin is white, but the commercial preparations are yellowish-brown wax-like solids, which are not soluble in water but form milky emulsions which exhibit the myeline figures under the microscope. The solubility in cold alcohol or ether is slight, but heat aids it. Lecithins are not soluble in acetone. They are hygroscopic and the water mixtures undergo decomposition on standing. They darken on exposure to air and light. The alcoholic solution is precipitated by platinum or cadmium chloride. It is decomposed by alkalies with the formation of choline and trimethylamine. The ash contains phosphoric acid. The different lecithins contain from 3.84 to 4.12 per cent. of phosphorus and 1.73 to 1.86 per cent. of nitrogen. The ratio of nitrogen to phosphorus should be at 1 to 2.21. Lecithin is incompatible with alkalies; it should be kept in well-stoppered bottles and should be protected from the light. The content of lecithin (plus kephalin) in tissues is about as follows: Per Cent. Egg-yolk 8 to 12 Egg-white 0.1 to 0.2 Liver 2.0 to 3.0 Kidney 2.0 to 3.6 Lung 2.0 to 3.0 Pancreas 2.0 to 3.0 _Actions and Uses._--The lecithin preparations have been recommended in many pathologic conditions, especially in malnutrition and sexual debility. Moderate doses are said to bring about a marked retention of nitrogen and phosphorus, but satisfactory proof of this is lacking. It is extremely unlikely that the small doses which have been recommended in pill or tablet form or in emulsions can have any perceptible action, in view of the fact that many of our natural foods contain much greater weights of available lecithins than the medicinal doses provide. There is no good basis for the statement that the free lecithin has a greater food value or is more readily assimilated than is the substance as found in eggs or tissue. The reverse proposition is much more likely to be true, especially when it is considered that the commercial preparations are usually somewhat altered or decomposed in the process of separation. _Dosage._--Given by the mouth in the form of pills, tablets or glycero-alcoholic emulsions. The amount of actual lecithin ingested in this way is usually small because of the doubtful purity of the original preparation. Several doses, as commonly administered, would be required to furnish the amount of lecithin present in a small egg.--(_From Reports of Council on Pharmacy and Chemistry, 1915, p. 122._) PROPRIETARY NAMES FOR LIQUID PETROLATUM Report of the Council on Pharmacy and Chemistry