Abstract
Twenty young rabbits, weighing from 600 to 800 grams, were each inoculated intravenously with 1/2 cc. of saline emulsion of a three weeks culture of virulent bovine tubercle bacilli. The emulsion contained about 35 bacilli to each oil immersion field. After 10 days, animals from this series were studied at bi-weekly intervals, to 6 weeks after infection, in the following manner:
Ten to 15 cc. of a 1 per cent normal saline solution of neutral red∗ was slowly injected into the ear vein. After 10 minutes the rabbit was quickly killed by air embolism. Thin slices of the lungs, which in most cases were well stained with neutral red, were fixed in Zenker-formol for 12 to 24 hours. Thin blocks of tissue (2 mm.) were quickly dehydrated, without washing, in acetone, cleared in benzene or xylol, and rapidly imbedded in paraffin.
Thin sections are then made and stained with carbol fuchsin and methylene blue. In the staining process both alcohol and water should be avoided as much as possible. The paraffin is removed by xylol, and the section transferred to acetone. It may then be passed rapidly through water, and washed quickly in Gram's iodine, or Lugol's solution, to remove most of the mercurial precipitate. After blotting dry, the staining with carbol fuchsin was performed on a warm plate in the usual manner. This process should not exceed more than one minute. This allows for rapid decolorization in acid alcohol which is essential, if the color of the neutral red in the section is to be preserved. The acid alcohol at the same time removes the iodine from the tissues. After quickly rinsing in water, the section is blotted dry, stained with Loeffler's methylene blue, decolorized slightly in 95 per cent alcohol, dehydrated further in acetone, cleared in xylol and mounted in balsam.
Get full access to this article
View all access options for this article.