424 Journal of Agricultural Research voi. xii, no. 7 



hours after giving thymol they were given calomel at the rate of 65 mgm. 

 for each 2.5 kilos of body weight. 



One of the dogs died immediately after receiving the thymol, and the 

 remaining two dogs each passed one ascarid. The post-mortem exam- 

 ination showed that one or both dogs were infested with hookworms 

 (Ancylostoma caninum), whipworms (Trichuris depyessiuscula), asca- 

 rids {Belascaris marginata), and Dipylidium caninum. The treatment, 

 therefore, proved an entire failure for all worms present except ascarids, 

 for which it showed a rather low degree of efficacy in this experiment. 



As the thymol used had not proved as efficacious against hookworms 

 as might be expected, a sample was sent to the Biochemic Division of 

 the Bureau for analysis. An analysis was made by Dr. Custis, who 

 reported that it responded to all tests for thymol and showed no impuri- 

 ties. Thymol is apparently a stable phenol; the writers are unaware 

 of any evidence indicating that it deteriorates. 



Since thymol in a single dose proved so ineffective in the foregoing 

 experiments, an experiment was undertaken to determine its efficacy 

 in repeated doses. Four dogs weighing 2.3 to 3.9 kilos were given a 

 preHminary purgation with 20 mils of castor oil on the day previous 

 to treatment and were then fasted for 24 hours. Thymol was given 

 at the rate of 130 mgm. per kilo of body weight, and this dose repeated 

 three and five days later for a total of three doses. After the second and 

 third doses of thymol, 97 to 130 mgm. of calomel were given. The first 

 dose of thymol was given dissolved in alcohol to one dog and resulted 

 in the immediate death of the animal. The other dogs were given the 

 thymol in aqueous suspension. 



The thymol removed 8 out of the 16 hookworms {Ancylostoma 

 caninum) present in the dogs, a rather poor showing in view of the pre- 

 liminary fasting, purgation, and repeated doses, but decidedly better 

 than in the previous experiments. It removed the only ascarid {Belas- 

 caris marginata) present and showed some slight degree of efficacy against 

 whipworms {Trichuris depressiuscida) . 



It appears from these three experiments that thymol to be at all suc- 

 cessful as an anthelmintic for hookworms {Ancylostoma caninum) must 

 be preceded by purgation and fasting and given in repeated doses. At 

 least two such courses of treatment should be given to remove the 

 greater number of the worms present, and further treatment combined 

 with prophylaxis is desirable. As a matter of fact, this is the usual 

 procedure in administering thymol in human practice, and it is usually 

 reaUzed by physicians that it is very difficult to remove all the hook- 

 worms present, as it is observed that hookworm eggs often persist in the 

 feces after repeated thymol treatments. 



In the three experiments considered together, thymol removed over 

 half thje ascarids present, but showed very little efficacy for whipworms or 



