In short, Formamint is recommended for the treatment or prevention of almost everything, from a bad breath to such grave conditions as scarlet fever, diphtheria and tuberculosis, conditions in which a delay in proper treatment--for instance, in diphtheria, a failure to administer antitoxin--may result in the death of the patient. A series of investigations was therefore undertaken in order to discover whether the extravagant claims regarding the germicidal power of Formamint could be verified. Experimental Data Two fifty-cent bottles of Wulfing’s Formamint were purchased in the open market and were kept well stoppered to prevent deterioration. Qualitative tests showed the presence of formaldehyd and the amount was determined quantitatively by the hydrogen peroxid method as given by Sutton.[23] The results were respectively, 1.99 per cent. and 2.03 per cent. of formaldehyd. [23] Sutton: Volumetric Analysis, Edition 10, p. 390. [Illustration: Two Formamint advertisements reproduced in miniature typical of those appearing in a certain type of medical journals.] Some determinations were made of the germicidal power of Formamint in vitro, that is, under controlled laboratory conditions. A twenty-four-hour plain agar culture of _Staphylococcus aureus_ was washed off in 10 c.c. of sterile 0.85 per cent. sodium chlorid solution. A 1:100,000 dilution of this was made in each of three flasks containing 100 c.c. of sterile saliva. Flask 1 contained 1 per cent. of Formamint, Flask 2, 5 per cent.; Flask 3, containing no Formamint, was kept as a control. At intervals samples were removed and dilutions made and plated in duplicate on standard agar. The plates were incubated twenty-four hours at 37 C., and plates containing less than 200 colonies were counted. The results are given in Table 1. After seven days there was no appreciable difference in the plates. Another test was made by adding a 1 per cent. Formamint solution to plain agar plates inoculated with _B. coli_. A twenty-four-hour plain agar culture of _B. coli_ was washed off in 10 c.c. of sterile 0.85 per cent. sodium chlorid solution. A 1:1,000,000 dilution was made of this and 1 c.c. added to each plate. Varying amounts of 1 per cent. solution of Formamint were added to each plate. They were incubated seventy-two hours at 37 C. After seven days’ incubation the count was the same. The results are given in Table 2.