
carbonic anhydrase by the subcutaneous administration of sul- 
fanilamide at levels of 0.16 ems. / kg. of body weight, thus 
confirming the results of previous workers. Mehrring et al. 
(1955) confirmed the hypothesis that the SOQoNHo group of the 
drugs 1s the inhibiting factor of carbonic anhydrase, by feed- 
ing to New Hampshire chickens two unsubstituted sulfonamides, 
Diamox and benzenesulfonamide. Both compounds caused the 
pullets to lay eggs with very thin shells or no shells at all. 
The sulfonamide group is the only chemical portion these two 
compounds have in common. 
c) The effects of Newcastle disease. 
Berg et al. (1947) indicated that Newcastle disease 
markedly decreases egg production, albumen quality, and shell 
thickness and smoothness. The authors observed that the loss 
in albumen quality as a rule was permanent and that the decrease 
in shell thickness may be affected for several months. Clegg 
and Muller (1951) showed that hens apparently recovering from 
the infection produced poor shells, although showing the normal 
serum calcium level for laying hens. The authors concluded 
that the poor quality of the shell was due to malfunction of 
the uterus produced by direct effect upon this region or upon 
disturbances of factors controlling shell secretion. Biswall 
and Morrill (1954) observed the same effects of Newcastte 
disease and also pointed out that although the rest of the re- 
productive system is susceptible to the virus, the uterus is 
the only section to suffer. functionally. 
d) The effect of various other compounds. 
Arasan: Arasan-SFX is a fungicidal agent used in 
treatment of seeds. It contains 75 per cent (T.M.1T.D.) tetra- 
methylthiuram disulfide. Swanson et al. (1956) feeding diets 
containing TMTD as low as 10 ppm. produced nearly 4 per cent 
eggs with very little shell or no shell at all. At levels of 
100 ppm. no hard-=shelled eggs were produced. Misshapen eggs were 
also observed at levels of 20 to 50 ppm. Recovery was complete 
after 2 days from withdrawal of the treated feed. 
5. Factors producing delayed or premature oviposition. 
Burrows and Byerly (1942) observed that intravenous 
injections of 2 units of obstetricial pituitrin in Rhode Island 
Red hens caused the premature expulsion of the eggs at any time 
after the egg had entered the uterus, but that eggs at higher 
oviducal levels were not laid prematurely. 
Sturkie and Weiss (1950) found that by intramuscularly 
injecting acetylcholine (10 mg. or higher) into hens which had 
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