CONSISTENCY OF COLLOIDS 71 



than gelatin. Gelatin may absorb about 25 times its weight in 

 water; fibrin 40 times. The order in which neutral salts act on 

 gelatin is different from that in which they act upon fibrin. 



It may be assumed that the different gels of the organism vary 

 quantitatively in their behavior under the influence of the same elec- 

 trolytes and it is obvious that the salt absorption of different gels 

 varies as well as their water absorption. An investigation of the 

 water and salt absorption of different kinds of gels in the presence of 

 mixtures of electrolytes is much to be desired. Our knowledge of 

 tissues and secretions forces us to the conclusion that the different 

 tissues possess a very different specific ability to absorb certain sub- 

 stances or ions. Only thus can we understand why the blood cor- 

 puscles withdraw more potassium salts from the lymph, the cartilages 

 more sodium salts and the bone-building tissues more calcium salts. 

 Only thus can we obtain a conception of the specific crystalloid con- 

 tent of various secretions and of selective resorption. 



The Crystallization of Colloids. 



Though P. P. VON WEIMARN describes the crystalline state as the 

 "sole ultimate condition of matter" which is characteristic 1 for all 

 substances (even gases), we shall not attempt here a critical study of 

 this theory nor determine the limits of the crystallization of solids. 

 We shall consider only how crystals occur in colloidal substances 

 and more particularly limit ourselves to the biocolloids. We know 

 only a limited number of crystallizable biocolloids; the most im- 

 portant are egg albumin, horse serum albumin, certain plant albumins 

 (aleuron crystals from Para nuts, cotton, hemp and sunflower seeds), 

 oxyhemoglobins, hemoglobin and methemoglobin. Egg albumin has 

 been obtained in the shape of needles, the albumins of vegetable seeds 

 partly in octahedra and partly in tablet-shaped hexagonal prisms. 

 Oxyhemoglobins crystallize in various ways depending upon the 

 animal species from which they are derived. For example, horse 

 oxyhemoglobin forms rhombic, and squirrel oxyhemoglobin forms 

 hexagonal prisms. These substances may be recrystallized and under 

 the same conditions give the identical crystal form. It may be re- 

 marked in passing, that many crystals giving the albumin reaction 

 have frequently been observed in organs, but they have been in- 

 sufficiently studied. [Crystalline form is markedly influenced by the 

 presence of protective colloids in the crystallizing solution. See J. 

 ALEXANDER, Kolloid Zeitschrift, iv, p. 86. Tr.] Crystalline products 

 have been obtained from starches, e.g., sphero-crystals from inulin. 



1 Bibliography given in Wo. OSTWALD'S Grundiss der Kolloidchemie (Dresden, 

 1911). 



