1 68 



PARAFFIN SECTIONING. 



\_CH. VII. 



ORDER OF PROCEDURE IN MAKING MICROSCOPICAL PREPARATIONS BY 

 THE PARAFFIN METHOD. 



§ 284. It will be seen from this table and from sections 268 to 283 

 that it requires from 7 to 10 days to get a microscopical preparation by 

 the paraffin method if one starts with the fresh tissue. Depending on 

 the method of fixing and hardening, the time may be much greater. 

 Unless much time is lost in waiting one must plan ahead in histological 

 work. 



1. Fixing and hardening the tissue or 



organ (g 269), 4 days or more. 



2. Dehydrating the object to be cut in 



95% or stronger alcohol (§ 270), 5 

 to 24 hours. 



3. Saturating the tissue with chloroform 



(I 271), 4 to 24 hours. 



4. In filtrating the tissue with chloroform 



paraffin (g 272), 3 to 10 days. 



5. Imbedding in pure paraffin (§ 273), 



10 minutes. 



6. Cutting the sections (§ 274), 10 min- 



utes. 



7. Fastening the sections to a slide 



(§ 275), 5 minutes. 



8. Removing the paraffin ($ 276), 10 



minutes to 24 hours. 



9. Washing in 95% alcohol to remove 



the benzin (§ 277), 2 minutes. 

 10. Staining with an alcoholic or aque- *9 

 ous dye (§ 278-279), 2 minutes to 24 

 hours. 



'3. 



14. 



15- 



16. 



17. 



18. 



Washing away the superfluous stain, 

 (§ 278-279). 



Staining with a general dye ( \ 280), 

 10 seconds to 10 minutes. 



Washing the sections with water or 

 alcohol (_\ 280), 3-5 minutes. 



Dehydrating the stained sections in 

 95% alcohol (\ 281), 5 minutes to 

 24 hours. 



Clearing the sections ($ 282), 5 min- 

 utes to 24 hours. 



Mounting in balsam ($ 283), 2 lo 5 

 minutes. 



Sealing the cover-glass ($ 238), 2 

 minutes. 



Labeling the preparation ($ 291), 2 

 minutes. 



Cataloging the preparation ($ 294), 

 5 to 10 minutes. 



SERIAL SECTIONS. 



*5 285. In histological studies it is frequently of the greatest advan- 

 tage to have the sections in serial order, then an obscure feature in one 

 section is frequently made clear by the following or preceding section. 

 While serial sections may be very desirable in histological studies, thev 

 are absolutely necessary for the solution of morphological problems 

 presented in complex organs like the brain, in embryos and in minute 

 animals where gross dissection is impossible. 



§ 286. Arrangement of Tissues for Sections in Histology.— 

 They should be so arranged that the exact relations of each part to the 

 organ can be readily determined. For example, an organ like the in- 

 testine, a muscle or a nerve, should be so arranged that exact transec- 



