The title that was assigned to me is a clear invitation to pontificate. Instead, I will share with you a few modest and not very original thoughts and speculations. These are based on a large literature and a small experience of tilling the soil among certain obscure and unnatural pyrimidines. This engage ment with the rationality of antimetabolites followed an ignoble exodus from the quagmire ...

By JANINE ANDRI -SCHWARTL I HE REJECTION of a skin homograft by the rabbit is accompanied by the proliferation of large, basophilic cells (hemocytoblasts) in its lymphoid system.1-2 These cells first appear in the lymph node contiguous to the homograft; later, they are found in regional and distant lymphatic structures, but they are always most prominent in the lymph node draining the homograft...

The importance of quantitative studies of the specificities of purine-metabolizing enzymes are discussed. These data not only enable one to make predictions concerning the metabolic disposition and effectiveness of a drug in vivo, but they also help to identify its loci of action. They may also serve as a basis for understanding the selective toxicity of a compound and aid in the design of new ...