(i) Nutrients: glucose, amino acids, vitamins etc.
(ii) Plasma proteins: albumin, fibrinogen, prothrombin, albumin, globulin etc. (7.5%).
(iii) Lubricants: neutral lipids, cholesterol, phospholipids, lecithin etc.
(iv) Pigments: bilirubin, biliverdin, carotene, xanthophyll etc.
(v) Organic acids: citric acid, lactic acid etc.
(vi) Excretory substances: urea, uric acid, creatinine, xanthine, ammonia etc.