PROTOPLASM 33 



ently structureless hyaloplasm that the real problem of cytoplasmic 

 organization lies" (Wilson, 1923). 



With the aid of a Spierer objective, which has a portion of the rear 

 surface of the front lens silvered, Seifriz (1931) has been able to see in 

 the hyaloplasm of onion cells a structure not hitherto reported. In the 

 optically empty ground substance ("cryptoplasm") there are dispersed 

 innumerable droplets of a grayish substance ("phaneroplasm"). The 

 cytoplasm thus has a finely mottled appearance. As the cytoplasm 

 streams, the phaneroplasm takes the form of parallel rods or continuous 

 strands 0.3 to OAfx thick and 0.2 to 0.3/i apart. It is the cryptoplasm 

 which appears to be the actively streaming component. 



The Colloidal State of Matter. — It is evident that many phenomena 

 in protoplasm are in some way dependent upon its ultramicroscopic 

 structure. It is here that cytology has received a notable contribution 

 from the field of physical chemistry in the form of facts and hypotheses 

 concerning the colloidal state of matter.-'^ 



Matter is said to be in the colloidal state when it is subdivided into 

 ultramicroscopic particles. Matter in which the particles are large 

 enough to be microscopically visible may show some of the properties of 

 colloids, but such properties are exhibited most characteristically when 

 the size of the particles lies between 0.1/x and Im/x. Such particles, or 

 "micelles," are generally groups of molecules, although it seems that they 

 may sometimes be single large molecules {e.g., in egg albumin). Although 

 they cannot be seen with the ordinary microscope, which reaches the 

 limit of its power with particles between 0.2ju and O.lix in diameter, their 

 presence may be indicated by the Tyndall phenomenon or by the ultra- 

 microscope, under which they appear as bright points against a dark 

 field. Wolfgang Ostwald (1917) gives the following table of diameters: 



Red blood corpuscle 7,500mM ( =7.5;u) 



Staphylococcus 800 



Particles in fine mastic suspension 500-1,000 



Casein particles in milk 130-170 



Colloidal gold particles 2-15 



Molecule of soluble starch 5 



Molecule of hsemoglobin 2.5 



Molecule of grape sugar 0.7 



Molecule of hydrogen 0.1 



The colloidal substance is, of course, enveloped in some other medium 



(gas, liquid, or solid), the two together constituting what may be termed 



a colloidal system. The subdivided substance is known as the "disperse 



phase," and the enveloping medium as the "dispersions medium." 



2° See Bancroft (1921), Bayliss (1915, 1923), Bechhold (1919), Czapek (19116), 

 Hatschek (1916), Lundeg&rdh (1922; Pt. I, Chap. XI), Meyer (1920; Chap. IV), 

 T. B. Robertson (1920), Lepeschkin (1924), Svedberg (1928), Freundlich (1928), 

 Gortner (1929), and Gray (1931). . 



