PIA MATER 



194 



PIROPLASMA 



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 about 100 cc. Transfer 

 directly to ammoniated 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 as mounting media (Wicks, 

 L. F., Carruthers, C. and Ritchey, 

 M. G., Stain Techn., 1946, 21, 121-126. 



Picric Acid is a very important ingredient of 

 several fixatives. It penetrates rapidly 

 and serves to some extent as a mordant 

 like potassium bichromate. See Bouin's 

 fluid. Picric acid staining of chromo- 

 phobe bodies of Lipschutz (Schiller, 

 Vir chow's Arch., 1930, 278, 663-689). 



Picro-Carmine (Ranvier) . There are many 

 sorts most of them based on Ranvier's 

 original formula: Add carmine (dis- 

 solved in ammonia) to sat. aq. picric 

 acid to saturation. Evaporate to j 

 original volume, cool, filter out ppt. and 

 evaporate filtrate to dryness. The 

 resultant red crystalline powder is 

 picro-carmine. Make a 1% aq. sol. for 

 staining. If overstained decolorize with 

 0.2% hydrochloric acid. This is an 

 excellent and very popular stain. It 

 colors keratohyalin very brightly (Lee, 

 p. 146). 



Picroformaldehyde Formic Acid tor fixation 

 (Lillie, R. D., J. Tech. Methods, 1944, 

 24, 35-36). Formaldehyde (37% solu- 

 tion), 10 cc, formic acid, 5 cc. and sat. 

 aq. picric acid, 85 cc. is recommended 

 as a substitute for Bouin's Fluid. It 

 decalcifies femurs of mice well in 48 

 hrs., provides sections adapted to 

 Romanovsky staining, and in general 

 acts like Bouin's fluid. 



Picro-Formol, see Bouin's Fluid. 



Picro-Indigo-Carmine is a much used stain. 

 Lee (p. 433) advises 3 parts sat. indigo- 

 carmine in 70% ale. and 1 part sat. picric 

 acid also in 70% ale. 



Picro-Mallory. Several fine modifications 

 of Mallory's connective tis.sue stain 

 using picric acid (McFarlane, D., Stain 

 Techn., 1944, 19, 29-37). 



Picro-Nigrosine for muscle. After alcohol 

 or Bouin fixation, stain sections in sat. 

 nigrosiue in sat. aq. picric acid. Muscle 

 yellow, connective tissue black. 



Picro-Suiphuric fixative, see Kleinenberg's. 



Pigments, general reviews: Bergmann, E. 

 Ergeb. d. Phvsiol., 1933, 35, 158-300; 

 Lederer, E., Biol. Rev., 1940, 15, 273- 

 306 (invertebrates). See Bacterial, 

 Bile Pigment, Bilirubin, Biliverdin, 

 Carotin, Carotinalbumins, Carotinoids, 

 Chromolipoids, Cytochrome, Hematin, 

 Hematoidin, Hematoporphyrin, Hemo- 

 fuscin. Hemoglobin, Hemosiderin, Tri- 

 chosiderin. Iron Pigments, Lipoclirome, 

 Lipofuscin (wear and tear pigment), 

 Malarial, Melanins, Parhemoglobin, 

 Porphyrins, Rhodopsin, Sulfmethemo- 

 globin. 



Pinacyanol (CI, 808) — sensitol red — A basic 

 xanthene dye of the cyanine group. 

 Proescher, F., Proc. Soc. Exp. Biol. & 

 Med., employed the Eastman Kodak Co. 

 product of which a 0.1-0.5% solution in 

 absolute ethyl or methyl alcohol for 5- 

 10 sec. stains frozen sections brightly. 

 Wash in water, mount in glycerine. 

 Chromatin, blue violet; protoplasm, 

 purple; connective tissue, red; elastic 

 tissue, black violet; muscle, bluish 

 violet to purple; amyloid, red; etc. 

 Hetheringtou, D. C, Stain Techn., 

 1936, 11,, 153-154, used pinacyanol as a 

 supravital stain for mitochondria in 

 blood cells. 



Pinocytosis, a term introduced by Lewis 

 (W.H., Bull. Johns Hopkins Hosp., 1931, 

 49, 17-26) to indicate drinking by cells 

 as opposed to phagocytosis, or eating by 

 cells. It means (Lewis, W. H., Am. J. 

 Cancer, 1937, 29, 666-879) microscopi- 

 cally visible drinking, not submicro- 

 scopic "sipping" v/hich Meltzer termed 

 "Potocytosis". By this process in tis- 

 sue cultures proteins and other sub- 

 stances that do not diffuse into the cells 

 are engulfed by wavy ruffle pseudo- 

 podia. The cell membrane, which first 

 invests the globulus of fluid taken into 

 the cytoplasm, later disappears and the 

 fluid becomes part of the cytoplasm. 

 Can be best seen in cultures of cancer 

 cells of which an excellent moving pic- 

 ture is available for distribution by the 

 Wistar Institute of Anatomy at Phila- 

 delphia. 



Piroplasma (L. pirum, pea + G. plasma, a 

 formed thing). Piroplasmas are pear 



