VALKONSKY METHOD 



376 



WALKER'S METHOD 



one or the other of these enzymes. 

 The chief metabolites of nicotinic acid 

 which are most abundant in human, 

 swine and dog urine, are N'-methyl- 

 nicotinamide and 6-pyridone. These 

 can be determined in a fluorometer 

 having a maximum transmission at 365 

 m^t in the ultraviolet (Johnson, 1949, 

 pp. 68-69). 



Paraminobenzoic acid. This vitamin 

 is unique among vitamins in that it 

 makes up an integral part of one of 

 the B vitamins, folic acid. Its nutri- 

 tional significance may depend on its 

 action as a building block of the folic 

 acid molecule. The catalytic action 

 of paraminobenzoic acid probably de- 

 pends upon this latter property. 

 P. Permeability factor (citrin), consid- 

 ered to be a minor water-soluble vita- 

 min. The active fraction of vitamin P, 

 extracted from lemon peels, is a mixture 

 of glucosides. Rutin is another flavone 

 glucoside isolated from tobacco leaves 

 and buckwheat which resembles vita- 

 min P in structure and activity. It 

 was first used clinically by Griffith, 

 J. Q., Couch, J. F. and Lindauer, M. 

 A., Proc. Soc. Exp. Biol. & Med., 1944, 

 55, 228-229 and since has been exten- 

 sively employed for the control of capil- 

 lary fragility. This vitamin may act 

 as a biological antioxidant for ascorbic 

 acid, or epinephrine, or it may inhibit 

 hyaluronidase activity. 



Volkonsky Method for mitochondria. This 

 is a complicated technique involving 

 staining with anilin fuchsin, aurantia, 

 methylene violet and azure II but can 

 give splendid results. See original ac- 

 count (Volkonsky, M., Bull, d'hist. 

 AppL, 1928,5, 220-222). 



Volume. As explained by Danielli (Bourne, 

 1951 p. 102), cell volume is a function 

 of the number of contained osmoti- 

 cally active particles unless change is 

 restricted by rigidity of the enveloping 

 membrane. A satisfactory technique 

 for measuring the volume of red blood 

 cells is to determine photoelectrically 

 light absorption of a suspension (Ja- 

 cobs, M. H., Biol. Bull., 1930, 58, 104). 

 The simplest way to obtain ratio for 

 cytoplasmic and nuclear volumes is to 

 outline nuclei and cytoplasms on koda- 

 loid and determine the weights as has 

 been recently done in carcinogenesis 

 (Cowdry, E. V. and Paletta, F. X., J. 

 Nat. Cancer Inst., 1941, 1, 745-759). 

 The technique, of course, varies with 

 structure involved, for example thyroid 

 colloid (Stein, H. B., Am. J. Anat., 

 1940, 66, 197-211), fresh endocrine 

 glands (Swinvard, C. A., Anat., Rec, 

 1939, 74, 71-78). To determine volume 

 and cell numbers in small organs 



(Dornfeld, E. J., et al., Anat. Rec, 

 1942, 82, 255-259). For influence on 

 tissue volume of various methods of 

 fixation, dehydration and imbedding, 

 see Stowell, R. E., Stain Techn., 

 1941, 16, 67-83. 

 Volume measurements 



1 liter = 2.1 U. S. pints (1.76 Imperial 

 pints) 



1 cc. = 16i minims (17 minims B.P.) 



1 gallon = 3.79 liters (1 Imperial gallon = 

 3.79 liters) 



1 pint = 473 cc. (1 Imperial pint = 568 cc.) 



1 fluid ounce = 29.5 cc. (1 fluid ounce 

 B.P. = 28.4 cc.) 



1 fluid drachm = 3.7 cc. (1 fluid drachm 

 B.P. = 3.5 cc.) 



1 minim = 0.065 cc. 



For accurate measurements in capil- 

 lary tube colorimetry and titrametric 

 techniques capillary tubes, pipettes, 

 microliter burettes and other instru- 

 mentation is required. These are de- 

 scribed in detail by Click 1949. To 

 measure the volume of irregular aspects 

 (0.01 to 1.0 M 1) a method of Holter, 

 H., C. rend. trav. lab. Carlsberg, S6r. 

 chem., 1945, 25, 156-167 is suggested. 

 This is a colorimetric technique, the 

 amount of color displaced by the ob- 

 ject being measured. 

 Volutin. Spherical bodies in fungi, bacteria 

 and other organisms (Taylor in Mc- 

 Clung's Microscopical Technique, p. 

 221). According to R. F. MacLennan, 

 in Calkins, G. N. and Summers, F. M., 

 Protozoa in Biological Research. New 

 York: Columbia University Press. 

 1941, 1148 pp., the term "volutin should 

 either be dropped or definitely re- 

 stricted to metachromatic granules 

 which respond to Feulgen's stain when 

 used without hydrolysis." 

 Volocidae, technique for, Hartmann, M., 



Arch. f. Protistenk., 1918, 39, 1. 

 Von Kossa, see Calcium. 

 Vulpian Reaction named after a Parisian 

 physician. Fresh slices of the adrenal 

 immersed in dil. aq. ferric chloride show 

 a green coloration of the chromaffin cells 

 of the medulla. It is a test for tissues 

 producing epinephrine. See : chromaffin 

 reaction and osmic acid. 

 Walker's Method for intestinal protozoa is 

 recommended as an excellent rapid 

 stream. However, almost equally satis- 

 factory results can be obtained by the 

 more tedious method of frequently 

 changing the water. Osmic acid con- 

 taining fixatives are to be washed in aq. 

 dest. for about an hour. After Regaud's 

 fixative the tissue is transferred to 3% 

 aq. potassium bichromate without wash- 

 ing in water. Tissues fixed in alcoholic 

 mixtures are to be briefly washed in 

 alcohol before dehydration. For de- 



