452 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



A search for this healmg agent was therefore attempted. On the 

 one hand was the intercstmg phenomenon of blowfly maggots appar- 

 ently producmg somethmg that stimulates healing m human wounds. 

 On the other hand was the biological certainty that maggots would 

 not do this merely to benefit their host. Throughout all nature no 

 organism does anything primarily to benefit an unrelated individual. 

 Any good effect arising from the association must be the result of a 

 secondary or involuntary act. In the case of maggots this would 

 include the function of excretion. As the fecal and urinaiy products 

 of maggots arc abundant and conspicuous, a study of them was 

 undertaken first. 



By means of a simple correlation the problem became further 

 clarified. In the first place, it was commonly known that the appli- 

 cation of macerated embryonic tissues to nonhealing wounds has 

 frequently hastened healing; and the presence of allantoic fluid in the 

 embryos suggested the main constituent, allantoin. 



It was also known that in the urine of many mammals allantoin is 

 present. True it had not been reported in insects, but uric acid, 

 from which allantoin is oxidized, is conspicuously present. With 

 these facts as a basis a search was made for allantoin in the excretions 

 of blowfly maggots. 



By the following procedure maggot excretions were readily ob- 

 tained in sufficient quantity to permit identification of allantoin: 

 Several thousand nearly full-grown maggots were reared under both 

 aseptic and nonsterile conditions. They were placed in glass funnels 

 which were stoppereil with cotton and half filled with small glass 

 beads to prevent overcrowding of the maggots. The maggots were 

 occasionally sprayed lightly with water from an atomizer to facilitate 

 drainage. The excretions were allowed to drip mto beakers for 3 to 

 4 hours. With sterile maggots aseptic technique had to be used 

 throughout the collecting process. A chemical analysis of the liquid 

 showed allantoui to be present. From 20 cc lots of both sterile and 

 nonsterile liquid, allantoin was separated in the crystalline condition, 

 purified, and finally identified by comparison of its melting point and 

 its optical crystallographic jiroperties with those of an authentic 

 sample.^ 



Interest was added to the investigation by finding about this time 

 an article by Macalister (1912) written 22 years previously in Eng- 

 land, stating that he had used allantoin successfully in the treatment 

 of chronic ulcers. He had obtained it from the roots of a plant 

 called comfrey. The origmal discovery of the healuig properties of 

 allantoin by MacaUster met with httle response at that time, and, 

 unfortunately, was soon forgotten. 



' The isolation and identiflcation of allantoin in these experiments were performed by Dr. E. P. Clark, 

 of the Division of Insecticide Investigations of the Bureau of Entomology and Plant Quarantine, and 

 Dr. G. L. Keenan, of the Food and Drug Administration, U. 8. Department of Agriculture. 



