42 THE CHEMISTRY AND PHYSICS OF THE CELL 



should probably be regarded as only topographical expressions, de- 

 noting two differentiated areas in a common structural basis." 



Because of the relative acidity of the nuclei they are electrically 

 negative to the cytoplasm, particularly when in karyokinesis, and the 

 chromatic elements of the nucleus can be shown to carrj'" a negative 

 electric charge."^- Sperm-heads in isotonic cane-sugar solution move 

 rapidly — ^2000 microns a minute — ^toward the anode, when a current 

 is passed through the solution; and leucocytes also go toward the 

 anode under the same conditions, the rate depending upon the pro- 

 portion of nucleoplasm and cytoplasm, large leucocytes sometimes 

 even going slowly toward the cathode. The SertoH cells of the testi- 

 cle, which have a round mass of cytoplasm with a number of minia- 

 ture spermatozoa heads at one side, orient themselves in the current 

 so that the side or end containing the spermatozoa drags the mass 

 of cytoplasm toward the positive pole. 



The Cytoplasm 



The cytoplasm, as before mentioned, contains all the primary 

 cellular constituents, and also such secondary constituents as the par- 

 ticular cell possesses. Nucleoproteins are undoubtedly present in 

 unknown proportions, but with the nucleic acid well saturated by 

 proteins, and perhaps also to a large extent combined with carbohy- 

 drates to form the glyconucleoproteins. Sometimes the nucleoproteins 

 of the cytoplasm may be partly of the unsaturated class, and show 

 an affinity for basic stains, as in the case of the Nissl bodies of the 

 nerve-cells, the basophilic granules of mast cells,^^ and perhaps also 

 the cytoplasm of plasma cells. The great question concerning the 

 cytoplasm is its structure — whether homogeneous, alveolar, areolar, 

 fibrillar, foam-like, or granular. On a previous page have been men- 

 tioned the experiments of Hardy, which show that homogeneous solu- 

 tions of protein, when fixed by the same reagents as are used in 

 the customary fixation of histological materials, may show quite 

 the same microscopical structures as are shown by the cytoplasm 

 of cells. Network, foam, and alveolar structures are produced in 

 albumin and gelatin solutions when they are hardened by bichloride 

 of mercury, osmic acid, formalin, etc., and the same characteristic 

 differences that are produced in cells by these different reagents are 

 likewise produced in the hardened protein solution. Protein struc- 

 tures hardened under strain form radiating structures resembling 

 centrosomes and the radiating threads seen in cells. If elder pith 

 is saturated with protein solutions and then hardened, sectioned, 

 and stained by the usual methods, appearances resembling closely 

 the structure of a hardened cell may be found in the spaces of the 



« Pentamalli, Arch. Entwick. u. Org., 1912 (34), 444; McClendon, Proc. Soc. 

 Exp. Biol, and Med., l'.)l() (7), 111; Hardy, .lour. Pliysiol., 1913 (47), lOS. 



