and Laboratory Methods. 11T9 



tissues are fixed in Miiller's fluid ; the object can have a large surface, but should 

 not be thick. From the fixation fluid the tissue is put into 70 per cent, alcohol, 

 as treatment with weak alcohol and water renders the fat unstainable. The 

 celloidin sections are put in the stain for twelve hours at a temperature of 40°C. 

 A 2 per cent, solution of Kultschitzki's haematoxylin (hematoxylin 2 gms., dis- 

 solved in a little absolute alcohol added to 100 c. c. of 2 per cent, acetic acid). 

 When the mixture, which is at first yellow, becomes red, it is ready for use. The 

 principal point is good decolorization, only well bleached preparations show the 

 fat clearly. The whole process is as follows : (1) Fix in Miiller's fluid 2 to 6 

 weeks, depending on the size of the object ; wash out in 70 to 85 per cent, 

 alcohol, etc., imbed in celloidin. (2) Cut sections 10 to 15 mikrons thick, and 

 put them directly from alcohol into the stain for twelve hours at a temperature of 

 40 °C. (3) Wash out with water. (4) Wash in a 1 per cent, solution of potas- 

 sium permanganate 10 to 15 minutes. (5) Wash in water. (6) Treat with a 2 

 per cent, solution of oxalic acid, or a mixture of two parts of 2 per cent, oxalic 

 acid to one of 2 per cent, solution of potassium sulphate, for five minutes. Should 

 the preparation show a yellow or gray-black color, return it to the potassium per- 

 manganate, then pass to the oxalic acid. If no fat is present the sections lose 

 their color entirely ; if fat is there the sections are light ash-gray to an intense 

 gray-violet, depending on the amount present. In this way fat is shown on a 

 colorless background in gray-violet fat globules. If it is desired to stain the 

 nuclei and protoplasm of the cells, a counterstain of concentrated carmin solu- 

 tion may be used as follows : (1) The sections decolorized in oxalic acid are 

 washed in water and left in an ammoniacal solution of borax carmin for twenty- 

 four hours. (2) Treated in acid alcohol (1 per cent, in 70 per cent, alcohol) for 

 two minutes, {o) Sat. alcoholic sol. of picric acid for one minute. (4) 85 per 

 cent, alcohol, absolute, xylol or origanum oil, balsam. The fat is now dark blue, 

 almost black ; nuclei, red ; protoplasm, yellow. This method is valuable for four 

 reasons : (1) Fat is clearly differentiated to the smallest particle. (2) This fat- 

 stain is very lasting; preparations remain good for several months. (3) Miiller's 

 fluid is an easily available fixation fluid. (4) The method is both inexpensive 

 and simple, requiring no complicated technique. a. m. c. 



RECENT LITERATURE. 



Lavdowsky, M. Ueber eine Chromsublimat- Nicolas, A. Recherches sur I'embryologie des 



verbinclung und ihre histologische Anwend- Reptiles. Contribution a I'etude de la 



ung, unter anderem audi zur Restauration Fecondation chez I'Orvet. Archiv. D'Anat. 



alterer Objecte. Zeit. f. wiss. Mikros. u. f. Micros. 3: 456-489, i pL, 1900. 



Mikros. Technik. 17: 301-31 1, 1900. Goodrich, E. S. Nephridia of Polycliasta. 



«; u i /-- .. •!- .• ' 1.'. J J 1 '. Quart. Jour. Micr. Sci. 43: 609-748, 6 pis., 



Weber, A. Contribution a 1 etude de la met- ^ ■' .^ /t > r 



amerie du cerveau anterieur chez quelques " ' • /-. 



Oiseaux. Archiv. D'Anat. Micros. 3 : 369- Yasuda, A. Adaptution of Infusorians to Con- 



424 2 pis. igoo. centrated Solutions. Jour. Coll. Sci. Tokyo. 



13: 101-140, 3 pis., 1900. 



