PHOTODYNAMIC ACTION 



269 



PICCOLYTE RESINS 



tainable from General Chemical Co., 

 New York) in 100 cc. aq. dest. and add 5 

 cc. glacial acetic acid. This dark green 

 solution soon becomes purple black but 

 is usable after many weeks. Rinse in 

 aq. dest. Stain, as above, with phos- 

 photungsticacid hematoxylin. 



Photodynamic Action of thiazine dyes on 

 vaccine virus may be due to red or infra 

 red rays (Hirano, N. and Sayama, K., 

 Arch. exp. Med., 1936, 13, 324-332). 



Photoelectric Colorimeter, construction and 

 use (Hanselman, R. C, Am. J. Clin. 

 Path., 1943, 13, 108-116). 



Photoelectric Microphotometer — Written 

 by R. E. Stowell, Dept. of Oncology, 

 University of Kansas Medical Center, 

 Kansas City 2, Kan. January 19, 

 1951 — The original type of apparatus 

 developed by Stowell, R. E. (J. Nat. 

 Cancer Inst., 1942,3, 111-121) was used 

 to measure the light absorbed as a 

 result of the specific coloration of tissue 

 components. Such equipment consists 

 of a light source, microscope, and photo- 

 electric equipment with amplification 

 and recording of light absorption. 

 Modified equipment is discussed by 

 Pollister, A. W. and Moses, M. J. (J. 

 Gen. Physiol., 1949, 32, 567-577). 

 Among substances measured by these 

 techniques are Feulgen reaction for 

 desoxypentose nucleic acid, pyronin 

 methyl-green stain for nucleic acids 

 and Millon's reaction for tyrosine. For 

 other possible uses of this type of equip- 

 ment see Stowell, R. E. (J. Invest. 

 Derm., 1945, 6, 183-189). 



Photoxylin, see Celloidin. 



Phrenosin is a Cerebroside. 



Phthalein Indicators. Table giving rela- 

 tive reactions of the several organs and 

 tissues after vital staining (Rous, P., 

 J. Exper. Med., 1925, 41, 739-759). 

 See Indicators of pH. 



Physiological solutions. These are in- 

 tended for the examination of living 

 cells with a minimum of change. Blood 

 serum, or plasma, is an unnatural me- 

 dium for any living cells except those 

 naturally intravascular as shown by the 

 fact that alone and undiluted it is a poor 

 medium for tissue culture. Physio- 

 logical saline is for mammals 0.85-0.9% 

 aqueous NaCl and for amphibians about 

 0.65% aqueous NaCl. For others see 

 Ringer, Ringer - Locke, Locke - Lewis 

 and Tyrode. Normal solutions (which 

 see) are different. 



Pia Mater. Perivascular nerves. Washout 

 blood by vascular perfusion with saline 

 solution or by rinsing nonperfused tis- 

 sue with saline. Fix with 10.5% citric 

 acid in 20% formalin preferably by in- 

 jection. Dissect out blood vessels of 

 pia under binocular microscope. Wash 



in aq. dest. twice and place in 20% aq. 

 silver nitrate 2 hrs. Pass through 4 

 changes 20% formalin in Petri dishes 

 each containing al)out 100 cc. Transfer 

 directly to ammoiiiated silver nitrate 

 made by adding cone, ammonia (28%) 

 drop by drop to 20% aq. silver nitrate 

 using 3 drops more than amount re- 

 quired to dissolve ppt. Observed under 

 the microscope the nerves "come up" 

 slowly and when they are dark enough 

 transfer to 20% ammonia water for 1-2 

 min. Wash in aq. dest. plus few drops 

 glacial acetic acid. Tone in 0.2% aq. 

 yellow gold chloride 30-60 min. Wash 

 in water, dehydrate in 3 changes 95% 

 alcohol, clear in carbol-creosote-xylol 

 mixture and mount in balsam (Penfield, 

 W., Am. J. Path., 1935, 11, 1007-1010); 

 revised by W. Penfield, Montreal Neu- 

 rological Institute, Montreal, Canada, 

 May 1, 1946. 



Pianese Method. Much used a generation 

 ago for study of cancerous tissue. 

 Pianese, G., Beitr. z. Path. Anat., u. 

 Allg. Path., 1896, Suppl. I, 193 pp. 



Piccolyte Resins — Written by L. F. Wicks, 

 Veterans Administration Hospital, Jef- 

 ferson Barracks, Mo. February 1, 

 1951 — These synthetic terpene resins 

 (/3 pinene polymers) have been recom- 

 mended for permanent mounting media 

 (Wicks, L. F., Carruthers, C. and 

 Ritchey, M. G., Stain Techn., 1946, 

 21, 121-126). Natural resins are quite 

 variable in quality, and with age the 

 poorer samples may turn yellow, crack 

 or develop acidity which fades basic 

 stains. Synthetic resins, being of con- 

 trolled manufacture, are much more 

 uniform in composition and predicta- 

 ble in behavior. An examination of 

 many such resins was stimulated by 

 the war-time scarcity of Canada bal- 

 sam. 



The requirements for a good mount- 

 ing medium are abbreviated from the 

 original article. It should possess: 

 1. Correct refractive index, 2. Freedom 

 from acidity, 3. Clarity, present and 

 future, 4. Solubility in the proper or- 

 ganic solvents, 5. Good adhesion for 

 glass, 6. Reasonable hardening time 

 (and not craze or granulate later), 7. 

 An approximately right softening tem- 

 perature, 8. Constant composition, 

 stability, inertness, availability and 

 moderate price. 



The Piccolytes meet all the above 

 stipulations, being of correct refractive 

 indices, very low acid numbers, pale, 

 non-yellowing, adherent to glass, and 

 soluble in .xylol and toluol. They are 

 also available in a variety of softening 

 points. Unfortunately, despite con- 

 siderable interest shown in the descrip- 



