Oct. 1.1924 
Critical Tests of Miscellaneous Anthelmintics 
317 
less toxic and less irritant to the mucosa 
than thymol and is better tolerated in 
the stomach. Such facts would favor 
this substance for use in place of thymol 
provided the anthelmintic efficacy 
were as high as that of thymol or 
higher. In experiments reported by 
Hall and Foster (13), thymol in doses 
of 4.5 to 26 grains administered in 
single and repeated doses to 9 animals 
removed 23 of 151 hookworms, or 15 
per cent, the maximum efficacy, 50 
per cent, being with doses of about 2 
grains per kilogram (or 20 grains for an 
average-sized dog) repeated three times. 
With these repeated treatments, 1 dog 
passed 89 per cent of its hookworms 
and the others passed none. Appar¬ 
ently neither thymol nor benzyl-phenol 
is very effective against hookworms in 
dogs, although the doses used, approxi¬ 
mately 2 grains per kilogram, or 1 
grain per pound, are those recom¬ 
mended for thymol for removing hook¬ 
worms from dogs. Both of these 
drugs appear much inferior to carbon 
tetrachloride for this purpose. 
TESTS OF ETHYLENE DICHLORIDE 
FOR WORMS IN DOGS 
PROTOCOLS 
Dog No. 617; 9.5 kg.; 2.85 cc. in 
hard capsules; first day, 2 hookworms; 
no worms the next 3 days; post¬ 
mortem, on fourth day, 21 hookworms, 
47 whipworms, 94 tapeworms. Drug 9 
per cent effective against hookworms; 
entirely ineffective against whipworms 
and tapeworms. 
Dog No. 645; 7 kg.; 3.75 cc. in hard 
capsules; no worms in 4 days; post¬ 
mortem, on fourth day, 3 hookworms, 
6 whipworms, 5 tapeworms. Drug en¬ 
tirely ineffective against hookworms, 
whipworms, and tapeworms. 
Dog No. 638; 14 kg.; 7 cc. by stom¬ 
ach tube; 1 hookworm and 1 whip¬ 
worm the second day; no other worms 
in 4 days; same amount then given in 
hard capsules; first day, 11 hook¬ 
worms; second day, 2 whipworms; no 
worms the next 2 days; post-mortem, 
on fourth day after second treatment, 
6 hookworms, 91 whipworms, 4 tape¬ 
worms. Two treatments 67 per cent 
effective against hookworms, 3 per 
cent effective against whipworms, en¬ 
tirely ineffective against tapeworms. 
DISCUSSION 
Chloroform has been more or less 
used in human medicine against hook¬ 
worms and has been especially recom¬ 
mended by Alessandrini (1). Schultz 
(39) found it effective in removing 
hookworms from dogs. Hall and Fos¬ 
ter (13) found it more effective in single 
dose for removing hookworms than 
other drugs tested by them and found 
its combination with chenopodium 
quite effective, as did Hall (16) in later 
experiments. The findings with chlo¬ 
roform, CHC1 3 , led Hall (18) to test 
carbon tetrachloride, CC1 4 , against 
hookworms, this drug being found more 
effective against hookworm in dogs than 
any other drug yet known. It is of 
interest in this connection to note that 
Caius and Mhaskar (4) found chloro¬ 
form very effective in removing hook¬ 
worms from man, and a year later (6) 
stated in connection with the efficacy 
of this drug: “This raises the question 
whether a narcotic, less toxic to the 
host than chloroform, assisted by a 
purgative, would not prove a very ef¬ 
ficient remedy for the removal of hook¬ 
worms.’ ’ The prophecy was fulfilled 
in the discovery of the value of carbon 
tetrachloride, Hall’s first paper (18) on 
this appearing the same month (April) 
as that of Caius and Mhaskar. Caius 
and Mhaskar later carried on tests of 
carbon tetrachloride, confirming its 
value against hookworms in man, and 
in a summary (7) they state that the 
value of carbon tetrachloride is corre¬ 
lated with the cumulative effect of the 
halogen atoms. On this bads ethylene 
dichloride, C 2 H 4 C1 2 , should rank some¬ 
where below chloroform as an anthel¬ 
mintic. In the present experiments 
this chemical in single doses of 0.3 to 
0.5 cc. per kilogram removed from 0 to 
9 per cent of the hookworms; and in 
two doses of 0.5 cc. per kilogram re¬ 
moved 67 per cent. These findings ap¬ 
parently sustain the theoretical like¬ 
lihood that this ethane derivative with 
two atoms of chlorine is less effective 
than the methane derivative, chloro¬ 
form, with three atoms, and this in 
turn is less effective than the methane 
derivative, carbon tetrachloride, with 
4 atoms of chlorine. The presence of 
hydrogen seems to increase the solu¬ 
bility of the chemical, carbon tetrach¬ 
loride being soluble 1 part in 1,250 of 
water and chloroform 1 part in 161 of 
water; the solubility of ethylene di¬ 
chloride is unknown to us but is probably 
closer to that of chloroform than to 
that of carbon tetrachloride. With the 
increased solubility there is an increase 
in undesirable systemic effects on the 
host animal, and a diminished efficacy 
against worm parasites. It may be 
concluded that ethylene dichloride 
shows a slight efficacy against hook¬ 
worms in dogs, as would be expected 
from its chemical composition; but 
