Cff. F/7] PREPARATION OF REAGENTS 203 



were tried, but not with so good success. (Proc. Amer. Micr. Soc., 1892, pp. 

 125-127). 



\ 328. Hematein. This is used iiistead of hematoxylin, as it is believed to 

 give more satisfactory results. Prepare as follows : Prepare a 5% solution of pot- 

 ash alum in distilled water and boil or leave in a steam steralizer an hour or two. 

 While this alum solution is warm add i per cent, of hematein dissolved in a small 

 quantity of alcohol. After the fluid has cooled add 2 grams of chloral for each 

 loo cc. of solution. (Freeborn, Jour. Ap. Micr., 1900, p. 1056. ) 



$ 329. Liquid Gelatin. Gelatin or clear glue, 75 to 100 grams. Commercial 

 acetic acid (No. 8) 100 cc. , water 100 cc., or glacial acetic acid 40 cc. and water 

 160 cc., 95% alcohol 100 cc., glycerin 15 to 30 cc. Crush the glue and put it into 

 a bottle with the acid, and set in a warm place, and shake occasionally. After 

 three or more days add the other ingredients. This solution is excellent for 

 fastening paper to glass, wood or paper. The brush must be mounted in a quill 

 or wooden handle. For labels, it is best to use linen paper of moderate thickness. 

 This should be coated with the liquid gelatin and allowed to dry. The labels may 

 be cut of any desired size and attached by simply moistening them, as in using 

 postage stamps. 



Very excellent blank labels are now furnished by dealers in microscopical 

 supplies, so that it is unnecessary to prepare them one's self, except for special 

 purposes Those like that shown in Fig. 163 may be had for about $4 for 10,000. 



I 330. Nitric Acid Dissociator. This is prepared by mixing So cc. of water 

 with 20 cc. of strong nitric acid. It is used mostly in dissolving the connective 

 tissue of muscle and thus making it possible to separate the fibers. Alum water 

 is used as a restrainer (314 and 264). (Proc. Amer. Micr. Soc., Vol. XI, ( 1889), 

 pp. 34-45). 



\ 33 r - Normal Salt Solution or Saline Solution. Pure water from its differ- 

 ing density from the natural lymph acts injuriously on the tissues. The addition 

 of a little table salt, however, prevents this deleterious action, or greatly lessens it, 

 hence the name of normal salt solution. It is a -$% solution of table salt (sodium 

 chlorid) in water ; water 1000 cc., salt 6 grams, or water 100 cc., salt T % gram. 



332. Paraffin. Paraffin is of various melting points, hence at the ordinary 

 temperature of a laboratory, that melting at the lowest temperature will be moder- 

 ately soft, hence soft paraffin, while that melting at a higher temperature will be 

 hard. For the best results one usually has to mix hard and soft paraffins. The 

 larger the object to be cut and the thicker the sections the softer should be the 

 paraffin. 



\ 333. Picric-Alcohol. This is an excellent hardener and fixer for almost all 

 tissues and organs. It is composed of 500 cc. of water and 500 cc. of 95% alcohol, 

 to which 2 grams of picric acid have been added. (It is a i% solution of picric 

 acid in 50% alcohol). It acts quickly, in from one to three days. ( 267, 284). 

 (Proc. Amer. Micr. Soc., Vol. XII (1890), pp. 120-122). 



\ 334. Shellac Cement. Shellac cement for sealing preparations and for mak- 

 ing shallow cells (\ 248) is prepared by adding scale or bleached shellac to 95% 

 alcohol. The bottle should be filled about half full of the solid shellac then enough 

 95% alcohol added to fill the bottle nearly full. The bottle is shaken occasionally 

 and then allowed to stand until a clear stratum of liquid appears on the top. This 

 clear, supernatant liquid is then filtered through absorbent cotton, using a paper 



