14 TECHNIC 



alcohol, 3 cubic centimeters; Giemsa's stain, 2.5 cubic centi- 

 meters. 



The stain should be poured over the slides immediately after 

 mixing, and should be changed twice during the first hour, and 

 allowed to remain in the third solution for twelve to eighteen 

 hours. The slides, which are heavily overstained by this 

 method, are differentiated in 95 per cent ethyl alcohol. The 

 procedure of differentiation really consists in removing the ex- 

 cess of stain to a point where good histological detail is secured. 

 If the sections are too blue, a better balance may be secured by 

 adding very small quantities of colophonium to the alcohol. 

 After differentiation the sections should be rapidly dehydrated 

 in absolute alcohol, cleared in xylol and mounted in oil of 

 cedarwood. 



The various steps in the technic are as follows: 



1. Fix in Zenker's fluid (formula: corrosive sublimate, 

 6 grams, potassium bichromate 2.5 grams). Twenty-four 

 hours should be allowed for animal tissues, but two to six hours 

 for louse tissues is sufficient. 



2. Embed in paraffin and section at 6ju or less. 



3. Xylol, alcohol, Lugol's solution; alcohol as usual. 



4. 0.5 per cent sodium hyposulphite to remove the last traces 

 of iodin, ten to fifteen minutes. 



5. Wash in running water ten minutes, followed by distilled 

 water. 



6. Stain, differentiate, dehydrate and clear as above, and 

 mount in oil of cedarwood. 



The staining of paraffin sections by Giemsa's stain is no more 

 complicated or difficult than using the eosin-methylene blue 

 stain. One condition, however, is absolutely essential, and that 

 is that the sections should be thin, not over six microns. 



