THE PARAFFIN METHOD 131 



indeed to injure a preparation at this stage of the process. Add a label, 

 and the mount is complete. 



A TENTATIVE SCHEDULE FOR PARAFFIN SECTIONS 



It will be useful to give several tentative schedules for the use of 

 beginners. It cannot be too strenuously insisted that these schedules 

 are only tentative, their sole object being to give the beginner a start. 

 The following is a tentative schedule for the ovary of a lily at any 

 period before fertilization. The pieces should not be more than 12 mm. 

 in length. 



1. Cliromo-acetic acid, 1 day. 



2. Wash in water, 1 day. 



3. Two and one-half, 5, 10, 15, 20, and 35 per cent alcohol, three grades a 

 day, morning, noon, and night; 50 and 70 per cent, change morning 

 and evening; 85 per cent, 24 hours; 95 per cent, all day or overnight; 

 absolute alcohol, 24 hours, changing 2 or 3 times. 



4. Mixtures of absolute alcohol and xylol; 2|, 5, 10, 15, 25, 50, and 75, 3 

 grades a day, morning, noon, and night; pure xylol, 24 hours, chang- 

 ing 2 or 3 times. 



5. Paraffin and xylol, 48 hours. 



6. Melted paraffin in the bath, 30-40 minutes, changing 2 or 3 times. 



7. Imbed. 



8. Section; about 10 /x is a good thickness. 



9. Fasten to the slide. 



10. Dissolve off the paraffin in xylol, 5 minutes. 



11. Xylol and absolute alcohol, equal parts, 5 minutes; 100, 95, 85, and 

 70 per cent alcohol, 5 minutes each. 



12. Stain in safranin (alcohoUc), 6 hours or overnight. 



13. Rinse in 50 per cent alcohol, using a trace of HCl if necessary; then 

 in 70, 85, 95, and 100 per cent alcohol, 5 minutes each. 



14. Stain in gentian violet dissolved in clove oil (or in clove oil with a httle 

 absolute alcohol), 10 minutes. 



15. Treat with pure clove oil until the gentian violet stain is satisfactory. 



16. Rinse in xylol, 1 minute. 



17. Mount in balsam. 



18. Label. 



That the paraffin method is tedious and complicated is universally 

 recognized. Many substitutes have been tried, but without enough 

 success to justify even a reference. 



