HYDROGEN ION INDICATORS 



123 



ILLUMINATION 



Indicator 



Litmus, purified 

 (Azolitmin) 

 1% aq. or 

 in agar sol. 



Neutral red 

 (Toluylene red) 

 1-2% aq. or sat. 

 in saline 



Cresol red 

 5.3 N/20 NaOH 



Metacresol purple 

 5.3 N/20 NaOH 



Thymol blue 

 4.3 N/20 NaOH 



HYDROGEN ION INDICATORS— Continued 



pH Range and Colors Remarks 



(approx.) red «— 6.0 — S.O-»blue Slow stain, diffuses poorly, usually de- 



posits in granules. 



(approx.) red «— 6.8 — 8.0 — > yellow- 



yellow <— 7.2 — 8.4 -♦ purple-red 



yellow <— 7.4 — 9.0 —► purple 



yellow <- 8.2 — 9.4 -♦ blue 



Very weak stain, precipitates out readily 

 in vivo, not toxic if pure. 



Somewhat toxic, not a strong staia. 



Very weak stain, not very soluble. 



Toxic, range too alkaline. 



Hydrokollag, a particulate material em- 

 ployed for injection of Lymphatic Ves- 

 sels which see. 



Hydrotropes, see Sudan Stains. 



Hydroxy Tri-Phenyl Methanes. These are 

 the rosolic acids. Amino groups of tri- 

 amino tri -phenyl methanes are replaced 

 by hydroxyls making them acidic in- 

 stead of basic. Examples : aurin (or 

 rosolic acid); red corallin. 



Hydroxybenzene Compounds as cytoplasmic 

 fixatives. Details of use of pj'rogallol 

 and resorcinol in neutralized formal- 

 dehyde solutions are given. The sim- 

 plicity and rapidity of the procedures 

 and the ease of thereafter cutting sec- 

 tions 1-2/x in thickness are cited as the 

 advantages special attention having 

 been paid to mitochondria and secretion 

 granules (Huseby, R. A., Proc. Soc. 

 Exp. Biol. & Med.. 1946, 61. 122-125). 



Hydroxyquinoline test for iron, see Iron. 



Hypophysis, see Pituitary. 



Ice-crysta! Artefacts in normal and chroma- 

 tolytic anterior horn cells (Gersh, I., 

 and Bodian, D., Biological Symposia, 

 1943, 10, 163-184). 



Icterus Index is a simple measure of the 

 degree of yellow color of blood plasma, 

 or serum, in comparison with standard 

 potassium bichromate solutions. Make 

 up in tubes of same thickness and bore 

 as hematocrit tubes a series of unit 

 dilutions of the bichromate solution 

 Unit 1 = 1 gm. potassium bichromate 

 in 10,000 cc. aq. dest.. Unit 3 = 3 gm. 

 in 10,000 cc, Unit 5 = 5 gm. in 10,000 

 cc. etc. The plasma of centrifuged 

 blood in hematocrit is compared with 

 these. If it has a color corresponding 

 to, say. Unit 5 of the bichromate solu- 

 tion the icterus index is considered to 

 be 5. The normal value of the icterus 

 index is usually given as 4-7 units. 

 The measure being that of color, and, 



since increase in color can be caused by 

 substances other than bilirubin, the in- 

 dex is not a specific measure of bili- 

 rubinemia. Lipochromes can increase 

 the index. If the blood is unusually 

 concentrated the index is higher al- 

 though the total amount of bilirubin in 

 the circulation may not be elevated. 

 See much more adequate description 

 by Wintrobe, M. M., Clinical Hematol- 

 ogy. Philadelphia: Lea & Febiger, 

 1942, 703 pp. 



Idiochromatin (G. idios, one's own, pe- 

 culiar). The chromatin concerned par- 

 ticularly with reproductive functions 

 such as chromosome formation con- 

 trasted with nutritive trophochromatin 

 (G. trophe, food, nourishment). There 

 is no special technique for it. 



Illumination. For microscopic work the 

 lighting is of great importance. Direct 

 visible light can best be obtained from 

 various electric microscopic lamps on the 

 market. Only when the light is more 

 intense than that required for routine 

 purposes can it be properly employed 

 for dark field examination or for polari- 

 zation. Therefore an intense source 

 should be available. The intensity can 

 be reduced to optimum by using an 

 iris diaphragm. When it is desired to 

 deliver light into the body to a position 

 behind living tissues or organs for 

 transillumination the Quartz Rod tech- 

 nique is suggested. 



Even to make the light equivalent in 

 quality to that from the white cloud on 

 a bright day, that microscopists used to 

 search for, is quite unnecessary. If the 

 light is too much screened by "day- 

 light" or other glass its intensity will 

 be impaired. Green light was recom- 

 mended quite enthusiastically about 20 

 years ago. But it is difficult to secure 

 green light of the necessary intensity 



