undulating and varicose and were often arranged in small bundlescontaining 3 6 axons the axons were very fine in caliber most of them being 1 4 microns in diameter since they were so close to the resolution of the light microscope we suspect that considerably greater invasion would be seen by electron microscopy when the slides were coded and randomized there was no difficulty in distinguishing between the specimens from the drug treated and the vehicle treated animals the most prolific nerve growth occurred in the animals treated with cytosine arabinoside and trea the animals treated with either trea or cystosine arabinoside also exhibited extensive nerve growth in comparison to the control examples 3 8 detail the preparation of pharmaceutical preparations for use in the present invention nerve regeneration is promoted by thoroughly bathing the injury site with the foregoing composition the foregoing composition promotes regeneration of damaged nerve tissue when administered directlly to the site of the injury nerve generation is facilitated when this composition is administered to damaged nerve tissue in quantities sufficient to bathe the injury site pharmaceutical compositions are prepared by adding to each of the compositions of examples 3 5 the nerve regeneration activity of each composition is superior to the activity of each composition without the addition of hepes pharmaceutical compositions are prepared by adding to each of the compositions of examples 3 5 the following the ability of each.