A major class of proteins found in the seeds of plants and in various tissues and substances of vertebrate and invertebrate animals, including blood, muscle, and milk. The globulins in blood comprise all the plasma proteins besides albumin. Two kinds, alpha and beta globulin, are primarily transport proteins or serve as substrates for forming other substances, and include lipoproteins and enzymes. A third kind, the gamma globulins, consists almost entirely of the immunoglobulins. Most globulins are insoluble in water but soluble in saline solution.