PHARMACOLOGY OP THALLIUM 
15 
all animals died, it is not possible to determine the minimum lethal 
dose from these data, except that it appeared to be less than 2.5 
grams of grain per kilo of body weight.^ No significance should be 
attached to the fact that white rats died from somewhat less than the 
smallest dose killing wild rats, as an insufficient number of animals 
were used to confirm this difference. 
Three white rats, weighing 190, 205, and 212 grams, respectively, 
were fed a mixture of 7.5 grams of paste and 7.5 grams of rat biscuit 
on July 25, 1924. All animals were in the same cage. Some of the 
paste was uneaten after 12 hours. The heaviest rat died on the third 
day; the other two showed extensive diarrhea and died during the 
night. 
On August 9, 1924, approximately 1 gram of paste was smeared 
on the back, between the shoulders, of each of six white rats. The 
rats were then placed in individual cages to prevent them from lick- 
ing poison from the backs of one another. Two days later, decided 
reddening of the noses of four was noted. On the fourth day 
three rats died, and the next day the other three died. Post-mortem 
examinations failed to show any abnormalities. 
This preliminary series of feeding experiments with the thallium 
grain and paste showed that wild and white rats died about three 
days after the consumption of comparatively small quantities of 
poisoned food. A series of experiments was then performed with 
chemically pure thallium compounds, to determine the nature of 
their action and the minimum lethal dose. 
SERIES 2 : CHEMICAIXY PURE THALLIUM SULPHATE 
A sample of chemically pure thallium sulphate was pulverized 
in a mortar and thoroughly mixed with screened rat food. Since 
thallium sulphate has the formula TI2SO4 and contains 81 per cent 
of thallium, 1.24 grams of thallium sulphate were taken as the equi- 
valent of 1 gram of thallium. 
Seventy-two white rats, weighing between 103 and 197 grams, 
were fed specified doses of thallium as sulphate, December 4 to 17, 
1924. Poisoned baits were consumed with the same eagerness as 
control food containing no thallium- In most instances all food 
was consumed within 15 to 30 minutes after exposure. The results 
obtained in this series of experiments are reported in Table 4. 
Twenty-five milligrams of thallium per kilo of body weight of rats 
(equivalent to 31 milligrams of thallium sulphate per kilo) killed 
73 per cent of the rats tested. All doses of 35 milligrams per kilo 
or larger, or an increase of 40 per cent in dosage, killed all rats. A 
dose of 20 milligrams per kilo, or a decrease of 20 per cent in dosage, 
killed about a third of the rats tested. Accordingly, 25 milligrams 
per kilo was selected as the minimum lethal dose. Confirmation of 
this value was obtained in another series of feeding experiments on 
May 9, 1927. Fifteen rats weighing 125 to 175 grams were fed thal- 
lium baits. (Table 4.) With a minimum lethal dose of 25 milli- 
grams of thallium per kilo when fed to rats, thallium proves to be 
more toxic than any of the ordinary rat poisons except strychnine. 
