46 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 showTi to carry 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 tlirough 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 Sertoli 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 of the primary cel- 

 lular constituents, and also such secondarj^ constituents as the particu- 

 lar 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 carbohydrates to form 

 the glyconucleoproteins. Sometimes the nucleoproteins o'f the cyto- 

 plasm 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, 

 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 mentioned the experiments of Hardy, which show 

 that homogeneous solutions of protein, when fixed by the same 

 reagents as are used in the customary fixation of histological mate- 

 rials, 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 char- 

 acteristic differences that are produced in cells by these different 

 reagents are likewise produced in the hai'dened protein solution. 

 Protein structures hardened under strain form radiating stmctures 

 resembling centrosomes and the radiating threads seen in cells. If 

 elder pith is saturated with protein solutions and then hardened, sec- 

 tioned, and stained by the usual methods, aiipearances resembling 

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

 the pith — even a central, niu'leus-like mass may be suspended in a 

 network of anastomosing threads. These and mnny other experiments 



33 Ppntamalli, .Arfli. Enlwicko. u. Orj:.. 1012 CM). Ill; :\I(( Iriuloii. Pror. Soc. 

 Exp. P.iol. and Med.. 1010 (7), 111: llanly. .Tonr. riiysiol,, 1013 (47). lOS. 



