
White Leghorn chickens were treated by injection into the 
albumin. Those compounds that produced the greatest mortality 
were not the natural moleties of vitamin Byp. Mortality varied 
with breed and season. The order in which the per cent 
mortality of the benzimidazoles occurred was much the same as 
that demonstrated for certain viruses, whereas the benezenes 
followed an inhibition pattern similar to that demonstrated 
for microorganisms which synthesize their own B,5 and/or 
riboflavins. 
The following steroids have been demonstrated to have 
adverse effects on the embryo only at the later stages in de- 
velopment, on or about the eighth day of incubation. 
Karnofsky (1951) stated that cortisone acted on the chorioal- 
lantoic membrane, thereby inhibiting growth and development. 
One mg. per egg produced a high mortality in the embryos tested. 
Danowski (1951) demonstrated that cortisone treated chick 
embryos excreted an excess of NaCl and reducing sugars into the 
allantoic fluid. He postulated that a negative electrolyte 
balance may play a part in producing the syndrome of the 
"sorisone effect". Evans (1953) and Sobel (1958) found that 
one mg. of cotisone injected at 8 days produced effects on the 
liver, gonads, eyes and feather growth. The greatest inhibition 
occurréd between the eighth and tenth days. 
van Tienhoven (1957) dipped eggs in 5 mg. of 
diethylstilbesterol in 100 ec. of o11 and in testosterone pro- 
prionate solution, 650 mg. T.P. in 100 ec. of ethanol. He found 
that hatchability was reduced 10 to 15 per cent with both 
treatments. . 
Certain chemical agents interfere with the synthesis 
of hormones. fThiourea and thiouracil are two such compounds. 
These compounds prevent the iodination of tyrosine and the pro- 
duction of thyroxine which are necessary for general growth and 
metabolism. Thiourea and thiouracil injected into the yolk sac 
of White Piymouth Rock chickens were found to have moderate yet 
important effects upon the embryo (Adams and Bull, 1949, and 
Grossowicz, 1946). At the eighth, fourteenth and eighteenth days 
of incubation, injections of thiourea and thiouracil produced 
an increase in the incubation period, lack of retraction of the 
yolk sac, decreased trunk and limb growth and obvious enlarge- 
ment of the thyroid gland. Romanoff and Laufer (1956) demon- 
strated that there is a difference in the effects produced in 
the embryo before and after for the thyroidcomes into function 
on the eleventh day (Hansborough and Khan, 1951). One of the 
effects, inhibition of gain in body weight, occurs only after the 
time of thyroid formation (Sinha, 1959). 
Compounds other than those of metabolic importance to 
the embryo have been tested as possible teratogens and inhibitors. 
Diazo dyes such as Trypan blue and Evans blue were found to have 
pronounced effects on rats and chickens (Wilson, 1955). 
43 
