[ To replace or supplement the matter in \ 264, 271, 280.] 



§ 271a. Displacing the Alcohol and Clearing Tissues with 

 Thickened Cedar-Wood Oil. (Lee p. 66, Neelsen and Schiefferdeck- 

 er, Arch. f. Anat. u. Physiol., 1882, p. 206). Instead of using chloro- 

 form as directed in § 271 much time is saved by displacing the alcohol 

 with thickened cedar-wood oil. When the alcohol used for dehydration 

 is displaced by the oil the tissue will look clear and translucent. It is 

 then removed from the cedar-wood oil and placed in pure, melted paraf- 

 fin and this is then put into a paraffin oven and left from 2 to 24 

 hours. It is then imbedded for sectioning (§ 273). The tissues are 

 not harmed by remaining a long time in the cedar-wood oil. Small 

 pieces of tissue are cleared by it and- made ready for paraffin infiltra- 

 tion in two hours or less. 



§ 274a. Extending the Sections with Warm Water. In section- 

 ing by the paraffin method the sections are very liable to be finely wrink- 

 led. These fine wrinkles or folds are very confusing. To remove them 

 the ribbons or separate sections as they are cut are placed on cold water in 

 a shallow basin. Then hot wateris slowly added till the sections extend 

 or straighten. This removes all the folds. When the water is cold 

 again the ribbons are cut up with fine scissors and the pieces transferred 

 to albumenized slides and treated as described in § 275. If the tissue 

 was stained in toto, no albumen or collodion need be used. The sec- 

 tions after an hour or more will cling very closely to the slide and may 

 be de-paraffined and mounted in balsam without the sections coming 

 off. (Gaskell, Quart. Jour. Micr. Science, xxxi (1890), p. 382; 

 Gulland, Jour. Anat. and Physiol, xxvi (1891), p. 56.) Where but 

 few sections are to be mounted on a slide, one may put them directly 

 from the knife to the slide, add enough water to float them, and heat 

 the slide gently. The sections will straighten ; the water may then be 

 drained off and the slide stood on end until the sections are dry and 

 adhere firmly. The sections appear more or less transparent when dry. 



§ 264a, 280a. Counterstaining with Picro-Fuchsin instead of 

 Eosin. For a general dye to use with hematoxylin, eosin is good, but to 

 differentiate the tissues more completely, especially connective tissue, 

 which is present in practically every section made, it is better to use Van 

 Gieson's Picro-Fuchsin. Formula : Saturated aqueous solution of picric 

 acid, 95 c.c., 1% aqueous solution of acid fnchsin, 5 c.c. Sections are 

 first strongly stained with hematoxylin, well washed with water and 

 then stained 15 seconds to 3 minutes in the picro-fuchsin. They are 

 then washed in water, dehydrated, cleared and mounted in acid balsam, 

 that is balsam that has not been neutralized. Neutral balsam soon 

 fades the red of the fuchsin. (See Freeborn, Trans. N. Y. Path. Soc, 

 1893, P- 73- Also studies from the Department of Pathology of the 

 College of Physicians and Surgeons, Columbia University, N. Y., 

 1894-1895.) 



