The individual members of these three groups may be arranged as follows on the basis of solubility, coagulability, etc.: I. SIMPLE PROTEIDS.--_A._ _Soluble in water._--_a._ Coagulable by heat, and by long contact with alcohol. Albumins: serum-albumin, egg-albumin, lacto-albumin, myo-albumin, vegetable albumins. _b._ Non-coagulable by heat and by long contact with alcohol. Proteoses:[51] protoproteoses, deuteroproteoses. Peptones:[51] amphopeptones, antipeptones, hemipeptones. [51] Used in the generic sense; the proteoses including albumoses, globuloses, myosinoses, elastoses, etc., and the peptones the peptone-products formed in the digestion of any or all proteids. _B._ _Insoluble in water, but soluble in salt solutions._--_a._ More or less coagulable by heat. Globulins. 1. Soluble in dilute and saturated NaCl solutions. Vitellins. 2. Soluble in dilute NaCl solutions, but precipitated by saturation with NaCl. Myosins, paraglobulin[52] or serum-globulin, fibrinogen, myo-globulin, paramyosinogen, cell-globulins. _b._ Non-coagulable by heat, soluble in dilute NaCl solution and precipitated by saturation with NaCl. Heteroproteoses. [52] Not completely insoluble in saturated NaCl solution. _C._ _Insoluble in water and salt solutions, soluble in dilute alcohol_--Zein, gliadins. _D._ _Insoluble in water, salt solutions and alcohol; soluble in dilute acids or alkalies._--_a._ Coagulable by heat when suspended in a neutral fluid. Acid-albumins, alkali-albumins or albuminates. _b._ Non-coagulable by heat when suspended in a neutral fluid. Antialbumids, dysproteoses, glutenins. _E._ _Insoluble in water, salt solutions, alcohol, dilute acids and alkalies; soluble in strong acids, alkalies, and in pepsin-hydrochloric acid and alkaline solutions of trypsin._--Coagulated proteids, fibrin.[53] [53] In blood-fibrin we have a good illustration of the fact that these divisions are not absolutely exact, since this form of proteid matter, for example, is somewhat soluble in dilute acids and in salt solutions, although requiring a long time for marked solution. II. COMPOUND PROTEIDS.--_A._ _Compounds of a proteid (globulin) with an iron-containing pigment, soluble in water and coagulable by heat and alcohol._ Hæmoglobin, oxyhæmoglobin, methæmoglobin, etc. _B._ _Compounds of proteids with members of the carbohydrate group. Insoluble in water; soluble in very weak alkalies._--_a._ True mucins. _b._ Mucoids or mucinoids. _C._ _Compounds of proteids with nucleic acid. Phosphorized bodies yielding by decomposition metaphosphoric acid. Insoluble in water and in pepsin-hydrochloric acid, but more or less soluble in alkalies._--Nucleins. _D._ _Compounds of proteids with nucleins. Very soluble in dilute alkalies._--Nucleoalbumins, as casein of milk, and nucleoalbumins of cell-protoplasm and cell-nuclei, etc. III. ALBUMINOIDS.--_A._ _Soluble in boiling water with formation of gelatin and yielding by decomposition leucin and glycocoll._--Collagen (gelatin).