GUM ARABIC — ^HEMATOXYLIN, DEL.\FIELD's 307 



from I to 3 minutes. Then it is rinsed in alcohol, transferred 

 to clove oil, and thence mounted in Canada balsam. A good 

 double stain is obtained if the clove oil has some eosin dissolved 

 in it. 



Gunther's modification of the Gram method is as follows: 

 The preparation is stained and passed through the potassium 

 iodide-iodine solution as above. Then it is placed for i to 2 

 minutes in alcohol, next for 10 seconds in a 3 per cent, solution 

 of hydrochloric acid in alcohol, then again for several minutes 

 in pure alcohol, until no more color comes away, and then it 

 is passed on into xylol, and finally is mounted in Canada balsam. 



Gum Arabic. — ^The study of the spermatozoids of ferns, 

 etc., is facihtated by adding a 10 per cent, solution of gum arabic 

 to the drop of water containing the spermatozoids, which are then 

 unable to move so rapidly in the thicker fluid. 



Hsematein. — Dissolve with heat i gm. of haematein in 50 

 c.c. of 90 per cent, alcohol, and add to this a solution of 50 gm. 

 of alum in i liter of distilled water. After cooling, filter if neces- 

 sary, and add a crystal of thymol to prevent the growth of fungi. 

 The solution is ready for use at once. Sections stained in this 

 solution should be washed in water and transferred to glycerine- 

 gelatine for mounting, or may be dehydrated and mounted in 

 Canada balsam. The stain may be reduced in overstained sec- 

 tions by allowing the preparation to stand for some time in a i 

 per cent, solution of alum. A sediment is apt to settle from this 

 solution, but this is not an indication that the stain is spoiled. 

 The sediment can be partly prevented by adding to the solution 

 about 2 per cent, of glacial acetic acid, which, on the whole, 

 increases the effectiveness of the stain. The acid should be 

 entirely washed from the sections with water before permanent 

 mounts are made. 



Haematoxylin, Delafield's. — Prepared by mixing 4 c.c. of 

 a saturated solution of haematoxylin crystals in absolute alco- 

 hol with 150 c.c. of a saturated solution of crystals of ammo- 

 nium alum in water. After standing for a week exposed to 

 the light and air, this should be filtered and mixed with 22 c.c. 



