100 GUIDE TO THE STUDY 



It should be heated until steam is given off (60 to 70°C.) 

 immediately before using. Handling slides with forceps or 

 allowing metal to come in contact with the solution in any way 

 must be avoided or precipitates will ruin the preparations. The 

 various stages may be outlined as follows: 



1. Prepare smear as above described. 



2. Fix in warm Schaudinn's fluid, 15 minutes. 



3. Rinse in 50 per cent alcohol, 3 to 5 minutes. 



4. Transfer to 70 per cent alcohol to which has been added enough 

 tincture of iodine to give a bright straw color, 10 minutes. If the fluid is 

 bleached, renew it. 



5. Harden in 95 per cent alcohol, 1 hour or more. 



6. Seventy per cent alcohol, 5 minutes. 



7. Fifty per cent alcohol, 5 minutes. 



8. Rinse in distilled water. 



9. Mordant in a 4 per cent solution of clear violet crystals of iron alum 

 (ammonio-ferric sulphate) in distilled water, 6 hours. 



10. Rinse in water. 



11. Stain in 0.5 per cent ripened solution of lnematoxylin in distilled 

 water, 6 hours to overnight. 



12. Rinse in water. 



13. Differentiate in 2 per cent iron alum solution, controlling by rinsing 

 in water and examining under the microscope from time to time. The 

 background should be grayish and it is desirable to differentiate the slides 

 to a slightly different degree since it is not feasible to search long for cysts 

 as controls. 



14. Wash in running water, or several changes, 20 minutes. 



15. Dehydrate, in 50, 70, 95 per cent and absolute alcohol, 5 minutes each. 



16. Clear in xylol, 5 minutes. 



17. Mount in Canada balsam. 



Instead of Canada balsam, euparol may be used as a mounting 

 medium and the material passed directly from 95 per cent 

 alcohol. Considerable economy results from the elimination of 

 absolute alcohol and xylol. 



Although the above method of preparing intestinal Protozoa 

 is tedious and time consuming, it usually gives better results 

 for inexperienced workers. 



Kofoid and Swezy, 1925, recommend a rapid method through 

 the use of alcoholic solutions: The stock solution 0.5 per cent iron 

 hematoxylin is diluted with 10 parts of 70 per cent alcohol, and 

 the stock solution of 4 per cent iron alum is diluted with 10 parts 

 of 50 per cent alcohol. The iron alum will not remain long in 

 solution in alcohol; hence the solution must be renewed frequently. 

 After the usual fixation in Schaudinn's fluid, followed by ascend- 



