432 HISTOLOGICAL TECHNIQUE. 



3. Stain with hsematoxylin and eosin (page 418), cutting short the 

 time of washing after the hsematoxylin, if in a hurry. 



4. Dehydrate in 95 per cent, alcohol ; two successive baths. 



5. Clear in carbol-xylol. 



6. Mount in xylol-dammar. 



Very serviceable sections can be prepared in less than twenty- 

 four hours by this method, and the specimens, though not of the 

 best quality, will be permanent, and may be kept for future refer- 

 ence. 



Special Methods. 



The foregoing methods are for the preparation of tissues from 

 which sections must be made before they are fit for examination 

 under the microscope. The physician is, however, frequently called 

 upon to examine other objects, when the following directions will be 

 found useful. 



1. Examination of Urinary and other Sediments. For the collec- 

 tion of the sediment vessels with vertical walls should be used, not 

 conical glasses. A test-tube answers very well. The sediment 

 should be allowed to settle for several hours in a cool place, to 

 avoid decomposition ; or, better, the sediment should be precipitated 

 by means of a centrifuge. It should be borne in mind that urine 

 becomes alkaline during decomposition, and that the ammonia pro- 

 duced causes changes in the characters of the crystalline or other 

 inorganic constituents of the sediment, and also renders the identi- 

 fication of the organic constituents difficult or impossible. 



When the sediment has collected at the bottom of the vessel a 

 portion should be removed with a pipette for examination. Place 

 the finger over one end of the pipette before introducing it into 

 the liquid, to retain the air, then place the other end in contact 

 with the sediment and allow the air to escape slowly by raising or 

 moving the finger a little. Close the upper end of the pipette and 

 withdraw it. Now carefully wipe the outside of the pipette and let 

 the fluid escape until a good sample of the sediment is at the end of 

 the tube. Place a drop of this sediment on a slide arid cover. Ex- 

 amine the specimen with a low power at first, taking care to use a 

 very small diaphragm. In this way the presence of urinary casts 

 may be more rapidly determined than if a high power is used. 

 When there is doubt as to a given object being a cast examine it with 

 a higher power. After the specimen has been examined for casts 

 and other objects large enough to be identified with a low power, 



