VISCOSITY 



371 



VITAL'STAINING 



ban and Schwarzenberg, 1939, 384 pp. 

 The "ultravirus" diseases of insects re- 

 quire special techniques and they 

 should not so often be ignored in ob- 

 taining a clear view of the viruses as a 

 whole. The following book is a mine 

 of useful information Paillot, A., L'ln- 

 fection Chez Les Insectes. Imprimerie 

 de Tr^voux, G. Patissier, 1933, 535 pp. 

 The Electron Microscope is of great 

 service in study of viruses. 



Botanists have greatly advanced 

 knowledge of the chemical composition 

 of viruses. Discussion by Bawden, 

 F. C, Plant Viruses and Virus Diseases. 

 Waltham: Chronica Botanica Co., 1943, 

 294 pp. of data bearing on the purity of 

 virus crystals, paracrystals and liquid 

 crystals shows the use and limitations 

 of present day techniques. His photo- 

 micrographs of the virus crystals are 

 interesting. The earlier literature is 

 well summarized. 

 Viscosity. According to Heilbrunn (L. V., 

 An Outline of General Physiology. 

 Philadelphia: Saunders, 1937), "Vis- 

 cosity can be roughly defined as the 

 force which tends to hold the particles 

 of a substance together when a shearing 

 force acting on the substance tends to 

 pull it apart." Viscosity is the in- 

 verse of fluidity. It is of great im- 

 portance to histologists to be able to 

 detect and if possible to measure changes 

 in viscosity. When a living cell is 

 examined in approximately an isotonic 

 medium and tiny particles in it begin 

 Brownian Movement a decrease in 

 viscosity is indicated and when the 

 movement ceases an increase is to be 

 expected. Thus Lewis (W. H., Bull. 

 J. Hopkins Hosp., 1923, 34, 373-379) 

 took cessation of Brownian movement 

 of particles in the nucleus viewed in the 

 dark field to mean gelation which is 

 increase in viscosity. A Microdissec- 

 tion method is to insert 2 microneedles 

 into a cell. If they can be pulled apart 

 easily the viscosity is low; if with diffi- 

 culty, it is high. The idea back of the 

 Ultracentrifuge method is that if two 

 cells of the same sort are subjected to 

 equal centrifugal force and a component, 

 say the nucleus, is displaced more in 

 one than in the other the viscosity of 

 the cytoplasm is greater in the cell 

 showing the least nuclear displacement. 

 But this is not necessarily true. One 

 has to be sure that the nuclei are of 

 equal Specific Gravity. If the more 

 displaced nucleus is of higher specific 

 gravity than the other it will be more 

 subjected than the other to the centrifu- 

 gal force and its greater displacement 

 will not signify a lower viscosity of the 



surrounding cytoplasm. Similarly if 

 the specific gravity of the cvtoplasm 

 surrounding the more displaced nucleus 

 is less than that in the other cell the 

 greater displacement subjected to the 

 centrifugal force of the nucleus through 

 it will not indicate a lower cytoplasmic 

 viscosity. When a material changes 

 from a sol to a gel its viscosity increases 

 without a change in specific gravity. 

 Consequently in the interpretation of 

 alterations in displaceability of cellular 

 components subjected to centrifugal 

 force one has to be on the lookout for 

 changes in specific gravity and col- 

 loidal state. For details in respect to 

 intranuclear viscosity, see Cowdry, E. 

 V. and Paletta, F. X., Am. J. Path., 

 1941, 17, 335-357; 1942, 18, 291-311). 



Vital New Red. This is an acid dis-azo 

 dye not listed in indexes but Conn (p. 

 64) calls attention to chlorazol fast 

 pink 4BL (CI, 353) as most nearly 

 resembling it. Vital new red is one of 

 the many dis-azo dyes employed by 

 Evans, H. M., and Scott, K. J., Car- 

 negie Inst. Wash., Contrib. to Embryol., 

 1921, 10, 1-56 to bring out a difference 

 in reaction of the two great groups of 

 connective tissue cells. 



Vital Red (CI, 456)— acid Congo R, azidine 

 scarlet R, brilliant Congo R, brilliant 

 Congo red R, brilliant dianil red R. 

 brilliant vital red — An important acid 

 dis-azo dye frequently used in standard 

 method for determination of blood 

 volume. 



Vital Staining. This technique has been 

 contrasted with Supravital Staining. 

 It must be viewed broadly. Any 

 nontoxic coloration of the living body is 

 vital staining. It is not restricted to 

 particulate materials or to colloidal 

 suspensions which are phagocytosed by 

 certain cells. The fat depots of an 

 animal become vitally stained red 

 when the said animal is fed fat colored 

 with alcohol soluble sudan III. Bone 

 formed while madder is available in 

 the circulation is stained red and dentin 

 is vitally stained violet by intravenous 

 injections of 1% sodium alizarin sul- 

 phonate (Gottlieb, B., Ztschr. f. Somat., 

 1913, 11, 452). The phthalein indi- 

 cators tint the tissues of living animals 

 faintly but almost all the colors of the 

 rainbow. Bile capillaries of the liver 

 can easily be stained by intravenous 

 injection of sodium sulphindigotate. 

 Many other examples of similar phe- 

 nomena could be cited. But it is 

 customary to think of vital stains as 

 substances which are regularly taken 

 in by cells of the Reticulo-Endothelial 

 System and by a few others on occasion. 



