54 Animal Microloyy 



Prepare a piece of intestine for staining in bulk (see vi). It should be 

 placed in the stain after thoroughly washing out the fixing reagent. 

 Preserve parts of it to cut in celloidin. Remove the lower jaw, and 

 prepare it for de-calcification of teeth as indicated in chap. xi. Likewise 

 prepare pieces of femur and of tar sal bone for sectioning (chap. xi). 



VI. STAINING IN BULK BEFORE SECTIONING 



It is sometimes desirable to stain objects before sectioning. 

 The method is a slow one, and requires stains which penetrate 

 evenly and thoroughly. Various preparations of carmine and 

 cochineal give the best satisfaction, although several hematoxylin 

 stains are also frequently used in this way. It is best to stain 

 immediately after fixing and washing out, before the object has 

 been carried into higher alcohols. In general, it is advisable to 

 section tissues and stain on the slide, because the staining can be 

 controlled more effectually. Use the piece of intestine already 

 prepared (see note above). 



1. After fixing in Gilson and thoroughly washing out in 

 water, place the tissue in borax-carmine for 24 hours. 



2. Wash in 35 per cent, alcohol for 5 minutes. 



3. Fifty, 70, 95 per cent, alcohols, 30 minutes each. 



4. From this point proceed through absolute alcohol, xylol, 

 and imbedding, sectioning, and mounting precisely as in the 

 general paraffin method, except that after the sections have been 

 freed from paraffin in xylol, do not mount immediately in balsam, 

 but first transfer the slide back into absolute alcohol, and thor- 

 oughly wash it in order to remove the glycerin from the fixative 

 and so prevent cloudiness of the final mount. From alcohol the 

 slide is passed through xylol, or carbol-xylol, and mounted in the 

 usual way. 



NOTE. When borax -carmine or Delafield's hematoxylin is used as 

 the stain for an entire object, the preparation usually needs to be 

 decolorized with acid alcohol. This may be deferred, however, until 

 after the object is sectioned. 



VII. PARAFFIN METHOD FOR DELICATE OBJECTS 

 To prevent the distortion of delicate objects which are to 

 be sectioned in paraffin the transition of the material from one 

 reagent to the other must be very gradual and the heat be mini- 



