T. S. intestine 



PARAFFIN SECTIONS 



131 



from the ribbon and mounted on the shde 

 in whatever manner has been selected. 

 Since the use of the conventional Mayer's 

 egg albumen (Chapter XXVIII V 21.1 

 Mayer 1880) has already been discussed, 

 another medium will be used. The hydro- 

 lyzed starch of McDowell and Vassos 

 (Chapter 8 V 21.1 McDowell and Vassos 

 1940) is very little known and well worth 

 using. The directions given in the i)lace 

 just cjuoted should be used in the prepara- 

 tion of this thick, viscous hquid of which 

 about four or five drops may then be 

 added to about 50 cc of distilled water in 

 an Erlenmeyer flask or beaker. The slides 

 must be cleaned before the sections are 

 mounted, and no two people have ever 

 agreed as to what is the most desirable 

 method of doing this. One way is first to 

 rub the shde briskly with 1 % acetic acid in 

 70% alcohol and dry it by waving in the 

 air. Other methods of cleaning the slide, 

 which yield equally good results can be 

 found from the index. Several drops of the 

 diluted adhesive are placed in the center 

 of each slide and one of the individual 

 sections then taken up with the tip of a 

 moistened brush and placed on the ad- 

 hesive. As soon as the section has been 

 placed on the fluid, the slide is lifted up, 

 warmed carefully over a spirit lamp until 

 the section is flat but the paraffin not 

 melted, and then the superfluous liquid 

 removed carefully with the edge of a filter 

 paper. The slide is then placed on a warm 

 table to dry and, if the drying period is to 

 be prolonged, it is as well to place a dust 

 cover over it, since grains of dust falling 

 upon the shde will adhere just as tena- 

 ciously to the adhesive used as will the 

 specimen itself. 



It is pi'ojwsed in the present example to 

 stain the slide in the simplest possible 

 manner with coelestin blue B followed by 

 phloxine. Various formulas for stains of 

 the coelestin blue B type will be found in 

 Chapter 20 under the heachng DS 11.41; 

 that preferred by the writer for its sim- 

 phcity is recorded as "Anonymous 1936." 

 There will also be required a solution of 

 phloxine for counterstaining. Phloxine ap- 

 pears to work best from a weak alcohol 

 solution. In Chapter 20 under the heading 

 of DS 12,2 will be found the suggestion 



that it be used in 0.2% solution in 10% 

 alcohol. Any of the other dyes thei-e rec- 

 ommended may, of course, be substituted. 

 Assuming the section now to be per- 

 fectly dry, it is turned upside down and 

 the light is reflected from it to see whether 

 or not the section is adherent to the glass. 

 If there is any air gap between the section 

 and the glass, a brilliant mirror will be 

 formed and, in a preparation as simple as 

 this, the shde had better be thrown away. 

 Having selected those slides which are per- 

 fectly adherent, they are then warmed 

 over a flame until the wax is melted and 

 diopped into a jar of xylene, where they 

 remain until the paraffin appears to have 

 been removed. They are then passed to 

 another jar of xylene where they remain 

 for at least five minutes, and then to a jar 

 of equal parts xylene and absolute alcohol 

 where they remain for a further five 

 minutes. This treatment is followed by 

 five minutes in absolute alcohol and then 

 by direct transference to distilled water. 

 After they have been in distilled water for 

 a few minutes, each slide should be lifted 

 and inspected to make sure that the water 

 is flowing uniformly over both the slide 

 and section. If it tends to be repelled by 

 the section, or a meniscus is formed around 

 the section, this is evidence that the wax 

 has not been completely removed, and the 

 slide must be transferred first to 95% 

 alcohol to remove the excess water, then 

 to absolute alcohol until perfectly dehy- 

 drated, and then through absolute to 

 xylene, where it remains until the wax has 

 been completely removed before being 

 brought down again as previously indi- 

 cated. The slides may be taken down one 

 at. a time and accumulated in distilled 

 water until they are required. When all 

 the slides have been accumulated in dis- 

 tilled water, they are transferred to the 

 coelestin B staining solution. The time in 

 this varies, but ten to fifteen minutes will 

 probably be sufficient to stain the nuclei. 

 One of the most useful features of this 

 stain is that it is almost imp()ssil)le to over- 

 stain in it. Sections may be left overnight 

 without staining the cytoplasm to a degree 

 which requires differentiation. After the 

 mu'lei are blue-black, therefore, or after a 

 time convenient to the operator hag 



