174 
Journal of Agricultural Research 
Vol. XXVII, No. 3 
Cresol in the compound solution used proved to be more effective than 
an aqueous solution of carbolic acid; a 3 per cent cresol solution (6 per 
cent liquor cresolis compositus) had the same results on fresh eggs as a 
5 per cent carbolic acid solution and was of greater value in the case of 
active embryos. A 1 per cent carbolic acid solution was too dilute to 
destroy the viability of fresh eggs when they were put in it for a 24-hour 
period; it is therefore not a satisfactory and practical disinfectant. A 
1 per cent cresol solution (2 per cent liquor cresolis compositus) proved 
effective for fresh, partially developed, or fully developed eggs when used 
for a 20-hour period. In this instance, however, it is clearly shown how 
important is the distinction between the exposure as carried out with a 
pure culture in a beaker and, on the other hand, under conditions where 
the eggs are mixed with sawdust. In the latter case neither a thorough 
spraying with 1 per cent cresol and subsequent standing of the mixture 
for 24 hours, or even a repetition of the treatment on the second day 
destroyed the vitality of the fresh eggs. This weaker solution of cresol 
is therefore not so practical as the 3 per cent solution. 
In regard to the relative efficiency of the disinfectants at 24 0 C. and 
at lower temperatures, the following was found to be true: 3 per cent 
cresol solution (6 per cent liquor cresolis compositus) worked as well at 
13 to 15 0 C. as at 24 0 C. with fresh eggs (5 hours’ exposure destroying 
their ability to develop), but with developed embryos, although at 24 0 C., 
it destroyed their activity in 5 hours, on the other hand, at from 5 0 to 
io° C. it did not do so even in a 16-hour period. With carbolic acid a 
5 per cent solution was not so effective on either fresh or developed eggs 
at refrigerator temperatures as at 24 0 C. 
As to the value of disinfectants in destroying Ascaris eggs in pig pens, 
it would appear that proper cleaning of the pens is a more useful and 
more economical method of eliminating the eggs or reducing their num¬ 
bers to a minimum than the use of disinfectants in the strengths and for 
the periods of time necessary to kill the eggs, assuming that thorough, 
application of the disinfectants can be secured under practical conditions. 
The thoroughness of application necessary as indicated by the experi¬ 
ments is such that it would probably not be commonly secured in practice. 
CONCLUSIONS 
Fresh and partially developed eggs of Ascaris lumbricoides show such 
very great resistance to low temperatures that subsequent development 
occurred even after the longest periods of exposure: With the fresh eggs 
a 40-day period at below zero Fahrenheit temperature (— 2° to —16 0 F.) 
and with the partially developed eggs a 20-day period at the same 
temperatures. The life of the embryos that developed in these eggs was 
in both cases relatively short, but in the second case their infectivity for 
guinea pigs was demonstrated. Developed embryos in Ascaris lumbri¬ 
coides eggs were killed by a 20-day exposure to such temperatures ( — 6° 
to —17 0 F.), but not by a 10-day period at the same temperatures nor 
by even a 30-day exposure to freezing temperatures above zero (12 0 
to 18° F.). It is therefore evident that while very low temperatures 
may have a destructive effect upon the vitality of Ascaris eggs, many 
eggs under natural conditions are likely to survive severe winter weather, 
and the cold of winter can not be depended upon to destroy the vitality 
of Ascaris eggs present in pens, pastures, stables, etc. It does, however, 
diminish their infectivity in the course of time and may aid in controlling 
