XENON 



381 



ZYMOGEN 



of tyrosine, phenylalanine or trypto- 

 phane in the protein molecule, and is 

 also given by all phenolic compounds. 

 Among the peptides, only the prota- 

 mines do not show a positive reaction. 

 To withstand the treatments, a strong 

 fixation is recommended, though the 

 reaction can also be performed on fresh 

 materials." See Purines. 



Xenon, see Atomic Weights. 



XL Carmoisine 6R, see Chromotrope 2R. 



Xylene Cyanol FF (cyanol FF). Related 

 to Aniline blue, an acid dye of the 

 phenylmethane series employed as 

 ultracellular indicator (Conn, H. J., 

 in McClung's Microscopical Technique, 

 1950, p. 103). 



Xylidine Ponceau 3RS, see Ponceau 2R. 



Xyloidin, see Pyroxylin. 



Yeasts, vital staining of, see Brilliant Pur- 

 purin R. Malachite green-safranin 

 technique for staining spores (McClung, 

 L. S., Science, 1943, 98, 159-160). 



Yellow M, seeMetanil Yellow. 



X-Ray Absorption of tissues provides 

 method of quantitative study of tissue 

 elements and their localization (Eng- 

 strom. A., Acta Radiologica, suppl. 53, 

 1946). This method has been ad- 

 vanced by Engstrom over that de- 

 scribed under Historadiography. It 

 has been much used in the quantitative 

 determination of the density of enamel 

 and dentin, see Boedeker, C. F. and 

 Appelbaum, E., Dental Cosmos., 1933, 

 75, 21. 



X-ray DifiFraction method for investigating 

 structure of nerve myelin sheath 

 (Schmitt, F. O., Bear, R. S. and Palmer, 

 K. J., J. Cell. & Comp. Physiol., 1941, 

 18, 31-42. See, also, Historadiography. 



Yaws. Treponema pertenue, 18-20 m long, 

 6-20 uniform spirals. Same technique 

 as for Treponema Pallida. 



Ytterbium, see Atomic Weights. 



Yttrium, see Atomic Weights. 



Zenker's Fluid. Potassium bichromate, 

 2.5 gms.; mercuric chloride, (corrosive 

 sublimate) 5 gms.; aq. dest., 100 cc; 

 glacial acetic acid, 5 cc. Because this 

 mixture does not keep well make a stock 

 fluid of say 2 liters by adding mercuric 

 chloride to saturation in 5% potassium 

 bichromate. It will do no harm if more 

 than sufficient mercuric chloride is used 

 and remains undissolved at the bottom 

 of the bottle. The main point is to reach 

 saturation. This will require several 

 hours unless the mercuric chloride is 

 dissolved in the aq. dest. with the aid of 

 gentle heat before adding the bichromate 

 which has been pulverized in a mortar 

 to facilitate solution. 



Immediately before use add 5% of 



glacial acetic acid. Fix tissues 24hrs. 

 and wash in running water about 12 hrs. 

 Dehydrate and imbed in the usual way. 

 Remove mercuric chloride from sections 

 by Lugol's iodine solution 5-10 min. and 

 wash out the iodine in alcohol before 

 staining. This fluid is employed in 

 techniques too numerous to mention. 

 It is called for in case of Mallory's Con- 

 nective Tissue stain and for demonstra- 

 tion of Tendons, Purkinje Cells, Muscle, 

 Fibrin, Hemofuscin, etc. 



Zenker Less Acetic is the stock solu- 

 tion without addition of acetic acid. 

 This will serve as a fixative for mitochon- 

 dria; because, since it does not contain 

 acetic acid, they are not dissolved. It 

 is, however, not recommended for mito- 

 chondria. 



Formalin-Zenker or Zenker-Formol 

 is a very useful fixative indeed. Helly's 

 fluid is Zenker with 5% formalin in place 

 of the 5% acetic acid. Maximow has 

 used 10% formalin instead of 5%. It 

 is added, like the acetic acid, just before 

 use. The time of fixation, washing, etc. 

 is the same as for Zenker's fluid. 



Ziehl's Carbol-Fuchsin (as emended Soc. 

 Am. Bact.): A. Basic fuchsin, 0.3 gm.; 

 95% ethyl alcohol, 10 cc. : B. Phenol, 5 

 gm.; aq. dest., 95 cc. Mix A and B. 

 Much used for the staining of Acid Fast 

 Bacilli. 



Zinc. Mendel and Bradley's Method (L. 

 B. and H. C, Am. J. Physiol., 1905, 

 14, 313-327). Treat paraffin sections 

 with 10% aq. sodium nitroprussate for 

 15 min. at 50°C. Wash carefully in 

 running water. Add cover glass. In- 

 troduce under it one drop potassium 

 sulphide solution which causes an in- 

 tense purple color (Lison, p. 98). 



Zinc Chloride, as substitute for mercuric 

 chloride in Zenker's fluid (Russell, W. 

 O., J. Techn. Meth. & Bull. Int. Assoc. 

 Med. Museums, 1941, 21, 47). 



Zirconium, see Atomic Weights. 



Zweibaum's Fixative. Add 1 part 2% aq. 

 osmic acid to 7 parts 3% aq. potassium 

 bichromate, 6 cc, 2% chromic acid, 3 cc. 

 and aq. dest., 5 cc. See Sudan Black B. 



Zymogen is substance within cells tliat 

 produces an enzyme (G. zyme, leaven 

 + gennao, I produce). It is usually 

 seen in the form of granules. These 

 zymogen granules as they occur in the 

 acinous cells of the pancreas, in the 

 chief cells of the stomach, in the serous 

 (or zymogenic cells of the salivary 

 glands and in other situations can be well 

 stained with Bensley's Neutral Gentian 

 or Bowie's Ethyl Violet-Biebrich Scar- 

 let. They can also be readily studied 

 in living cells and their behavior noted 



