78 THE CELL. 



pure xylol, and finally in paraffin. The tissues imbedded in paraffin 

 must not be cut thicker than i to 2 p.. 



Altmann mounts according to the following method : A rather thick 

 solution of caoutchouc in chloroform (the so-called traumaticin of the 

 Pharmacopeia i vol. guttapercha dissolved in 6 vols. chloroform) is 

 diluted before use with 25 vols. of chloroform and the resulting mixture 

 poured upon a slide. The latter is tilted, and after evaporation of the 

 chloroform, heated over a gas flame. The paraffin sections are mounted 

 upon the slides so prepared and then painted with a solution of guncotton 

 in aceton and alcohol (2 gm. guncotton dissolved in 50 c.c. of aceton, 

 5 c.c. of which is diluted with 20 c.c. of absolute alcohol). After painting 

 with this solution, the sections are firmly pressed upon the slide with 

 tissue paper, and after drying are made to adhere more closely by slight 

 warming. Fixation to the slide with water is equally good. The sections 

 can now be treated with various staining solutions without becoming 

 detached from the slides. The paraffin is gotten rid of by immersing in 

 xylol, after which the specimens are placed in absolute alcohol. Fuchsin S. 

 can be used as a stain (20 gm. fuchsin S. dissolved in 100 c.c. anilin 

 water). A small quantity of this solution is placed upon the section, 

 and the slide warmed over a flame until its lower surface becomes quite 

 perceptibly warm and the staining solution begins to evaporate. The 

 slide is then allowed to cool, washed with picric acid (concentrated 

 alcoholic solution of picric acid diluted with 2 vols. of water), after 

 which it is covered with a fresh quantity of picric acid, and again, but 

 this time vigorously, heated (one-half to one minute). Occasionally 

 the same results can be obtained by covering the section for five minutes 

 with a cold solution of picric acid of the above strength. This last 

 procedure has a decided influence upon the granula, and gives rise to a 

 distinct differentiation between them and the remaining portions of the 

 cell, the latter appearing grayish -yellow, while the granula themselves 

 appear bright red. In some cases where the granula can not be sharply 

 differentiated from the remaining structures, it may be necessary to 

 repeat the staining process. Xylol-Canada balsam should not be used 

 for mounting, as it has a bleaching effect upon the osmic acid in the 

 specimen. Mount either in liquid paraffin (Altmann) or in undiluted 

 Canada balsam, which is easily reduced to a fluid state, whenever needed, 

 by heating. 



There is another method used by Altmann which deserves mention, 

 but practical application of which must be improved upon in the future ; 

 this consists in freezing the specimens and drying them for a few days in 

 the frozen condition in a vacuum over sulphuric acid at a temperature of 

 about 30 C. 



According to Fischer, dilute solutions of pepton when treated with 

 various reagents (especially with a potassium bichromate-osmium mix- 

 ture) form precipitates and granules which are remarkable in that they 

 react to stains exactly as do Altmann 's granula. It is, therefore, doubt- 

 ful whether Altmann 's granules should be regarded as vital structures. 



Altmann (92) has also devised a simpler negative method for 

 demonstrating the granula. Fresh specimens are placed for twenty-four 

 hours in a solution consisting of molybdate of ammonium 2.5 gm., 

 chromic acid 0.35 gm., and water 100 c.c. ; then treated for several 

 days with absolute alcohol, sectioned in paraffin, and colored with a 

 nuclear stain such as hematoxylin or gentian. The intergranular network 



