PHARMACOLOGY OF THALLITTlVt 
17 
on November 25, 1927, representing acceptable and nonacceptable 
material employed by E. E. Horn, of the Biological Survey. His 
descriptions of these samples show the degree of success obtained in 
using them under field conditions : 
Sample No. 1. — Taken from supply furnished during November, 1926. This 
material was absolutely refused when applied on steam-crushed oats at Flag- 
staff, Ariz., early in May, 1927. It was but slowly eaten at the Vallecito 
Ranger Station, Colorado (La Plata County, Zuni prairie dogs). It was slowly 
accepted by the Gunnison prairie dogs in Moreno Valley, N. Mex., during 
July, 1927, and was refused by Plains prairie dogs at Tatum, Lea County, N. 
Mex., during August, 1927. The trials at Tatum were under conditions of 
extreme summer heat. Acceptance in Moreno Valley, N. Mex., was slower than 
in a supply obtained by A. E. Gray and used during July, August, and September 
of the same year. 
Sample No. 2. — From a supply furnished in April, 1926. During the spring 
of 1926 at Flagstaff, Ariz., this material was readily accepted and gave excel- 
lent results in controlling Zuni prairie dogs. In the spring of 1927 it Was 
refused at Flagstaff, at Vallecito Ranger Station (Zuni prairie dogs), and in 
the Moreno Valley (Gunnison prairie dogs). In the summer of 1926 the 
material was a pure gray white, but in 1927 many yellowish flakes were notice- 
able in the product. This material was recieved and kept in a tin container. 
Sample No. 3. — From a small supply received by the laboratory from S. E. 
Piper in California during September, 1927. No information is available here 
as to the source, but it is labeled " Thallium Sulphate — German production — 
thallium sulphate 99 per cent, inert material 15." This sample was received 
too late to be used for field tests of acceptability. Earlier German products 
were highly acceptable and of uniform toxic effect. 
Sample No. 4- — A sample of thallous carbonate received during the late 
summer of 1926. It was liighly acceptable to the Zuni prairie dogs at Flagstaff, 
Ariz., during August and September, 1926, and was readily taken by Gunnison 
prairie dogs in the Moreno Valley of New Mexico during a time when some of 
the sulphate salts were refused. At Tatum, N. Mex., during August, 1927, 
the carbonate was better accepted than the various sulphate samples, but was 
of too low acceptability to be of value. (Weather very hot. Extreme drought 
during part of tests, and summer rains occurring during the latter part of 
operations.) 
Sample No. 5. — Thallous sulphate furnished to the Arizona district during 
the summer of 1926. This material was held over and used for the first time 
in the spring of 1927. Under prevailing spring winds refusal resulted. D. A. Gil- 
christ noted and reported an offensive odor in the material. This was removed by 
the American Smelting and Refining Co. chemists by heating to 150' C. for 
30 minutes and placing in glass containers. After the spring winds subsided 
all baits were accepted with avidity. 
Sample No. 6. — This sample has not been tried out in field operations but 
an analysis and feeding test are desired of it in order to ascertain its chemical 
purity, which would serve as a guide in possible future purchases of thallium 
sulphate. 
Samples 1, 2, 4, and 5 came from one American manufacturer; 
sample 6 from another. Unsuccessful attempts were made to ar- 
range for chemical analyses of these samples. Pressure of other 
work prevented feeding experiments until April 10, 1928, when doses 
of 20 and 40 milligrams of each sample were fed to three rats each. 
The rats ranged in weight from 145 to 355 grams. All baits were 
prepared to contain 0.5 per cent of thallium salt (0.4 per cent of 
thallium). Observations were continued over seven days, during 
which time all the rats died. (Table 5.) This prevents the accurate 
determination of the lethal doses of the respective samples. The 
fact, however, that all rats fed 20 milligrams per kilo died does 
prove that these samples were as toxic as the chemically pure thal- 
lium sulphate used in series 2. 
