THE FOLIC ACID GROUP 595 



aqueous suspension of infected tissue into the breast of baby chicks on 

 an ordinary diet resulted in development of tumors in approximately 95 

 per cent of the chicks; but out of 40 similarly injected chicks on a folic 

 acid-deficient diet, no tumors developed. However, the frequency of tumor 

 development with chicks on the same deficient diet but injected daily with 

 folic acid (100 y), pteroyl-a-glutamylglutamic acid (500 y), pteroyltri- 

 glutamic acid (500 y), or N 10 -methylfolic acid (100 y) was 90, 90, 100, 

 and 80 per cent, respectively. No such action was noted with similar 

 injections of pteroyl-D-glutamic acid, pteroic acid, pteroylaspartic acid, 

 N 10 -methylpteroic acid or p-aminobenzoyltriglutamic acid. 



On a normal diet on which 95 per cent of the chicks developed tumors 

 by the twentieth day, folic acid antagonists tended to prolong or com- 

 pletely inhibit the development of the tumor, but were in many instances 

 rather toxic to the host. Thus, daily intraperitoneal injections, begin- 

 ning at the time of inoculation with tumor of 5-6 day old chicks, of 

 4-amino-4-desoxypteroyl-L-aspartic acid (400 y), 4-amino-4-desoxy- 

 pteroyl-D-glutamic acid (400 y), 4-amino-N 10 -methyl-4-desoxypteroyl- 

 glutamic acid (100 y), and 4-amino-N 10 -methyl-4-desoxypteroic acid 

 (100 y) decreased the percentage of chicks developing tumors by the 

 twentieth day to 40, 0, 70, and 60 per cent, respectively. Pteroylaspartic 

 acid and pteroyl-D-glutamic acid did not exhibit any appreciable in- 

 hibitory activity on the tumor. Concentrations of the compounds which 

 were inhibitory to tumor growth resulted in impairment of health and 

 eventual loss of life, particularly when the compounds were injected. The 

 therapeutic index was slightly more favorable in older animals and least 

 favorable with one-day old chicks. The method of administration was 

 also important, and the best results were obtained on administering the 

 antagonists in the diet. Thus, 80 mg per kg of diet of 4-amino-4-desoxy- 

 pteroylaspartic acid or a similar amount of 4-amino-4-desoxypteroyl-D- 

 glutamic acid was relatively nontoxic to one-day old chicks, and prevented 

 for 17 days the development of tumors in 75 and 55 per cent of the chicks, 

 respectively. All the untreated controls developed tumors. 



4-Amino-4-desoxyfolic acid is suitable only for treatment of adult birds 

 since it is extremely toxic for growing chicks. Any concentration affecting 

 tumor growth was lethal to the chick. However, 1 mg of 4-amino-4- 

 desoxyfolic acid, administered daily by intraperitoneal injection, pre- 

 vented the development of the tumor in approximately 60 per cent of 

 adult birds as compared with 20 per cent obtained with 4-amino-4-desoxy- 

 pteroylaspartic acid administered similarly. Even at this dosage for adult 

 birds, 4-amino-4-desoxyfolic acid produces noticeable emaciation in adult 

 birds, and a few injections of 10 y are lethal to baby chicks. Doses of 

 0.25 mg of folic acid, pteroyltriglutamic acid or pteroyldiglutamic acid 



