16 TECHNICAL BULLETIN 2 3 8, U. S. DEPT. OF AGRICULTURE 
Table 4. — Toxicity of thallium as sulphate to white rats, 1924 and 1927 
EXPERIMENTS IN 1924 
Da<?e of 
thallium 
Number of rats dying after 
per kilo- 
gram of 
body 
weight 
Rats 
fed 
1 day 
2 days 
3 days 
4 days 
6 days 
Total deaths 
Mg. 
10 
Number 
10 
Number 
0 
Per cent 
0 
15 
8 
1 
1 
12 
20 
8 
2 
1 
3 
37 
25 
11 
2 
4 
1 
8 
73 
35 
5 
3 
2 
100 
50 
5 
1 
2 
2 
5 
100 
75 
5 
3 
2 
5 
100 
150 
5 
3 
2 
5 
100 
250 
5 
1 
4 
5 
100 
500 
5 
2 
3 
5 
100 
1,000 
5 
4 
1 
5 
100 
EXPERIMENTS IN 1927 
20 
5 
1 
2 
3 
60 
25 
5 
1 
4 
5 
100 
30 
5 
5 
5 
100 
It was noted that death usually occurred on the second or third 
day after feeding thallium bait, unless the quantity of poison taken 
Avas excessive. Ten times the lethal dose killed only one out of 
five rats within one day; 40 times the lethal dose killed only four 
out of five rats within one day. This would indicate that thallium 
must be absorbed from the gastrointestinal tract and localized within 
the tissues before producing death. For rats, at least, thallium is 
a definite poison, but not a rapid one. 
Results obtained with the thallium-treated grain in series 1 sug- 
gested that the minimum lethal dose of the grain was 2.5 grams per 
kilo, or possibly somewhat less. Results obtained in series 2 showed 
that the minimum lethal dose of thallium as sulphate is 25 milligrams 
per kilo. Accordingly, it would appear that the grain fed contained 
25 milligrams of thallium on 2.5 grams of grain, or 1 per cent of 
thallium. This has not been confirmed chemically. The exact lethal 
dose of the grain was not determined ; it is conceivable that it might 
be lower than 2.5 grams per kilo, which would proportionately 
increase the thallium content. It appears safe to conclude, however, 
that the thallium-treated grain as fed contained at least 1 per cent 
of thallium. 
SEEIES 3 : COMMERCIAL THALLIUM PBEPAKATIONS 
Commercial supplies of thallium compounds were obtained by the 
Bureau of Biological Survey for use in controlling prairie dogs 
and ground squirrels in the West where strychnine baits had been 
refused by the rodents. It was soon found that some particular 
shipments of thallium products were rejected when mixed with the 
usual baits, although other lots were taken readily and effectively. 
xV set of six samples was transmitted for examination and analysis 
