20 TECHNICAL BULLETIN 2 3 8, U. S. DEPT. OF AGRICULTURE 
beings exhibit the same symptoms as animals, alopecia being the most 
pronounced symptom. 
Thallium has been abandoned for treatment of night sweats of 
phthisis because of its toxicity. Under carefully guarded conditions 
it may be of value in the production of alopecia in the treatment of 
ringworm in children, when doses of 8 milligrams per kilo of body 
weight arc given under a physician's direction and observation. 
TqxIc reactions are frequently obtained with a dose of this size or 
even smaller. 
Information in the literature confirms the conclusion of Swain and 
Bateman {1^1) that " Thallium deserves to be classed among the 
most toxic of the elements." 
LABORATORY EXPERIMENTS WITH RODENTS 
By the standardized method developed for preparing and feeding 
poisons to rats, about 2.5 grams of a sample of commercial thal- 
lium-treated grain per kilo of body weight was found to kill wild 
and white rats in three to four days. Approximately 1 gram of a 
paste containing thallium caused death in the same time, when 
applied to the skin of the back. The minimum lethal dose of 
chemically pure thallium sulphate was found to be 25 milligrams 
of thallium, or 31 milligrams of thallium sulphate per kilo, when fed 
to rats. Death usually occurred on the second or third day. Six 
commercial thallium preparations were studied; some of them had 
been refused by prairie dogs in field tests, while other lots had been 
taken readily. All samples killed rats at 20 milligrams per kilo and 
were consumed with equal readiness. 
Within 24 hours after consuming a fatal dose of thallium, rats 
became restless and lost their appetite, and difficulties in breathing 
developed, which terminated in death from respiratory failure. 
Post-mortem, congestion of the heart, liver, and lungs and sometimes 
of the kidneys and spleen was noted. Rats surviving sublethal doses 
of thallium showed alopecia 10 to 15 days after feeding. 
Intravenously injected into the marginal ear veins of rabbits, 25 
milligrams per kilo of thallium was found to be the minimum lethal 
dose. 
CONCLUSIONS 
Although thallium has been employed in human medicine in doses 
of 8 milligrams per kilogram of body weight, its use is dangerous 
and is decreasing. 
The minimum lethal dose of thallium, fed as the sulphate to wild 
or to white rats, is 25 milligrams per kilogram of body weight. 
Death usually occurs on the second or third day after feeding and 
is due to respiratory failure. 
Thallium affects the sympathetic nervous system, thereby pro- 
ducing general alopecia (loss of hair), pains in the muscles and 
nerves of the legs, and disturbances of the endocrine glands (par- 
ticularly the ovaries and testicles and the thyroid, suprarenal, and 
pituitary glands). Calcium metabolism is upset and leads to rickets. 
Injected intravenously into rabbits, the minimum lethal dose is 
25 milligrams per kilogram. 
