and Laboratory Methods. 1493 



Mix the two solutions, then add the stain, stirring thoroughly. As soon as 

 the stain is all dissolved, filter. This solution keeps well, gives all the staining 

 reactions, and may be diluted to any degree with distilled water without causing 

 precipitation. The above method of preparation must, however, be rigidly 

 followed. 



Tissue may be fixed in any way, but formalin, mercuric chloride, and Zenker's 

 give the best results in the order named. Parafiin or celloidin embedding may 

 be used. Excellent results may be obtained by the combination plate-method. 



Staining method (Morse) : 



1. Stain 1-5 minutes. 



2. Wash thoroughly in distilled water. 



3. Blot with filter paper. 



4. Anilin-Xylol (2:1). 



5. Pure Xylol. 



6. Balsam. 



This method is the best one for the reactions with the majority of patholog- 

 ical substances. The variations of this method for certain specific reactions 

 will be mentioned below. Nearly all the tissues of the body and the important 

 pathological conditions have been worked over with this stain. Its most impor- 

 tant applications are as follows : 



For use as a simple nuclear stain it is best to stain only two minutes, then 

 wash and differentiate in alcohol. A contrast stain is not necessary, as the deep 

 violet color of the nuclei is easily distinguished from the pale blue tint given to 

 other structures. Eosin may, however, be used after the sections have been 

 stained and differentiated in alcohol. 



Blood smears give the best results when fixed as for tri-acid staining. Heat 

 fixation gives the best result. When stained for two minutes the red cells are a 

 light yellowish green, the protoplasm of the leucocytes colorless, and the nuclei 

 rose-pink. Blood-plates and basophile granules stain like the nuclei. The mala- 

 rial Plasmodium stains a dull pink, not as deep as the leucocyte nucleus, and is 

 easily distinguished. In well fixed tissue sections blood stains similarly, but the 

 basophile granules do not show. 



The nuclei of young connective tissue stain a light purple, while the intercel- 

 lular substance takes a dull rose pink; in old connective tissue the nuclei stain a 

 deep violet or purple, while the intercellular substance does not stain at all or 

 takes a very light violet. 



Yellow elastic tissue stains a sky blue. It is best brought out by longer 

 staining. 



Voluntary muscle stains a pale green with violet nuclei, the protoplasm of 

 involuntary muscle a light purple to a light blue with nuclei of a darker shade. 



Nerve cells and axis cylinders stain purple, the nuclei violet, the granules of 

 the cell body are very distinctly shown. Neuroglia stains a very light purple, or 

 not at all. 



Fibrin stains a bluish purple, but this reaction is not distinctive. 



Hyalin in corpora fibrosa does not stain at all or takes faint blue tint. 



Colloid takes a deep indigo blue, which is very characteristic. 



