PALITZSCH'S BORAX-BORIC 



185 



PARAFFIN EMBEDDING 



French, R. W. Stain Techn., 1930, 5 

 87-90; 1932, 7, 107-108 recommended 

 the use of these buffers for the range pH 

 9.2-8.2 but he made them up in a dif- 

 ferent way. 



Palladium. Histochemical detection based 

 on reaction between palladium and p- 

 Dimethylaminobenzyl-idenrhodanin in 

 neutral formalin or alcohol fixed tissues 

 (Okamoto, K., Mikami, G. and Nishida, 

 M., Acta Scholae Med. Univ. Imp. in 

 Kioto, 1939, 22, 382-387). 



Panchrome is a modification by Pappenheim 

 (Folia haematoL, Arch., 1911, 11, 194) 

 of the Giemsa stain. Add 0.75 gm. of 

 the panchrome powder (G rubier) to 75 

 cc. pure methyl alcohol and 25 cc. acid 

 free glycerin at 60°C. After filtering 

 keep in glass stoppered bottle. Use 

 after May-Griinwald fixation as de- 

 scribed for Giemsa after methyl alcohol 

 fixation. According to Slider and 

 Downey (McClung's Microscopical 

 Technique, p. 329) it gives better 

 coloration of neutrophilic granules and 

 metachromasia of mast granules than 

 the plain Giemsa's stain but "some 

 delicacy is lost, and the cells are more 

 likely to be muddy." 



Pancreas. This organ lends itself very well 

 to microscopic examination in the fresh 

 state. The classic which everyone seek- 

 ing technical details should consult is 

 Bensley, R. R., Am. J. Anat., 1911, 12, 

 297-388. The techniques for Blood 

 Vessels and Nerve Endings are those 

 employed generally and are described 

 under these headings. No particular 

 difficulties will be encountered in their 

 adaptation to the pancreas. It may be 

 helpful however to consult Beck, J. S. 

 P. and Berg, B. N., Am. J. Path., 1931, 

 7, 31-35 on the blood vessels. The 

 same holds for the Connective Tissue 

 components. Epithelial parts of the 

 pancreas can routinely be examined in a 

 preliminary way with the other parts in 

 tissues fixed in Formalin-Zenker and 

 stained with Hematoxylin and Eosin. 

 For details see Zymogen, Ducts and 

 Islets of Langerhans. 



Pancreatin digestion method for spleen 

 (Kyes, P., Am. J. Anat., 1901, 1, 37- 

 43). 



Paneth Cells. Influence of fasting on 

 (Klein, S., Am. J. Anat., 1905-1906, 5, 

 315-330). To observe storage and dis- 

 charge phases examine in guinea pigs 24 

 and 6 hrs. after feeding (Klein, S., Am. 

 J. Anat., 1905-06, 5, 315-330). By com- 

 bining DeGalantha's amyloid stain with 

 mucicarmine, Paneth granules are col- 

 ored green and mucous granules red 

 (Hertzog, A. J., Am. J. Path., 1937, 

 13, 351-360). 



Pantothenic Acid. Detection by fluores- 

 cence microscopy in tomato plants 



(Bonner, J. and Dorland, R., Am. J. 

 Bot., 1943, 30. 414-418). 



Pappenheim, see Panchrome, Kardos-Pap- 

 penheim, Methyl Green-Pyronin and 

 May-Giemsa Stains. 



Para Red (CI, 44) is useless as a stain (Emig, 

 p. 30). 



Parabenzoquinone, as a fixative for mito- 

 chondria (Baker, J. R., Nature, 1932, 

 130, 134; Sircar, S. M., J. Roy. Micr. 

 Soc, 1935, 55, 238-244). 



Paracarmine (Mayer). Dissolve 1 gm. car- 

 minic acid, 0.5 gm. aluminium chloride 

 and 4 gms. calcium chloride in 100 cc. 

 70% alcohol. Warm slightly, if required. 

 Allow to settle and filter. Tissues to be 

 stained should not be alkaline or con- 

 tain much lime (Lee, p. 147). 



Paraffin Imbedding. For routine it is more 

 convenient than celloidin imbedding. 

 Thinner sections can be cut and it is 

 easier to make them in series. Paraffin 

 imbedding is quicker and the blocks 

 being dry are easily stored in a smaller 

 space. 



After the specimen has been cleared 

 (see Clearing) it is placed in paraffin 

 held at a temperature just sufficiently 

 high to keep it melted. For ordinary 

 purposes a paraffin with melting point 

 of 56-58°C. is employed; but 60-62°C. 

 is sometimes selected for very thin sec- 

 tions and 52-54°C. for thick ones. 

 Paraffins of low melting points are de- 

 scribed by Waterman, H. C, Stain 

 Techn., 1939, 14, 55-62. When it is 

 desired to give the imbedding medium 

 more firmness than 60-62 °C. paraffin, 

 use is occasionally made of Rubber 

 Paraffins or Ceresin. Under Clarite 

 is described a mixture of paraffin and 

 clarite for use in hot weather when thin 

 sections are demanded. Routine paraf- 

 fin infiltration is best done in wide 

 mouthed glass bottles or jars in an in- 

 cubator held at the proper temperature. 

 Excessive temperatures harden and 

 shrink the tissues. The paraffin over 

 each specimen should be changed at 

 least once to insure removal of the xylol 

 or other clearing agent. If this removal 

 is incomplete difficulties will be later 

 encountered in crystallization of the 

 paraffin block and in sectioning. The 

 time necessary for infiltration will de- 

 pend on the size of the tissue and its 

 penetrability. Five to 6 hours is about 

 the average with limits of 2 to 24 hours 

 in special cases. See special treatment 

 for Teeth and Bone. 



For actual imbedding, folded paper 

 containers have now been rather gen- 

 erally replaced by glass dishes. Watch 

 glasses (Syracuse preferred) are satis- 

 factory ; but Petri dishes, the inner sides 

 of which are not quite vertical but slope 

 outward slightly from the base, are bet- 



