320 HISTOLOGICAL TECHNIQUE. 



pernicious anaemia. The presence of iron in this pigmentation may 

 be demonstrated by the following method : 



(a) The tissues should be fixed in alcohol. 



(6) Soak the section in a 2 per cent, solution of potassium ferro- 

 cyanide for ten minutes. 



(c) Transfer to Orth's acid alcohol (page 290) for five or ten 

 minutes. 



The sections may now be examined in a glycerin-mount with a 

 wide diaphragm, or they may be counterstained, for which purpose 

 treat as follows : 



(d) Wash with water. 



(e) Stain with Orth's lithio-carmine. 



(/) Dehydrate and mount in xylol-dammar. 



The iron in the section is converted into Prussian blue ; the nuclei 

 of the cells, when the counterstain has been employed, are red. 



/. Examination of sputa for elastic fibres. In pulmonary disease 

 involving a destruction of pulmonary tissue and the appearance of 

 fragments in the expectoration, elastic fibres from the alveolar walls 

 may frequently be found in the sputa : 



Fill a test-tube one-third full of sputa, add five or six drops of 

 36 per cent, potassium hydrate solution, and boil the mixture for 

 three or four minutes. Add an equal bulk of distilled water. 

 Divide the contents of the tube between the two tubes of the cen- 

 trifuge and precipitate their contents. If elastic fibres were pres- 

 ent, they will be found either in the sediment or in the scum on the 

 top of the fluid. 



3. Methods of Maceration. — 



a. One-third alcohol. 



95 per cent, alcohol, 35 cc. 



Distilled water, 65 " 



This dilute alcohol is excellent for the separation of epithelium 

 from the surfaces of mucous membranes. The fresh tissues are 

 placed in the alcohol for a day or two, after which the cells can 

 easily be detached and separated by shaking. The cells are well 

 preserved, and may be stained with methylene-blue or alum-car- 

 mine. 



b. Potassium hydrate. 



Potassium hydrate, pure by alcohol, 36 grams. 



Distilled water, 64 cc. 



