LIFE HISTORY OF ASCARIS LUMBRICOIDES. 7 
observations have been made as to the slight effect upon Ascaris eggs 
of various substances that are very destructive to protoplasm. For 
example, Galli-Valerio (1914) succeeded in developing the eggs to 
a stage containing vermiform embryos in solutions of sulphuric, hy- 
drochloric, nitric, and acetic acids 50 per cent or less in strength, in 
saturated solutions of copper sulphate, iron sulphate, and copper 
acetate, and in 50 per cent antiformin. In experiments with full- 
strength antiformin we have found that the shells of eggs contain- 
ing motile embryos are dissolved by this substance, but the thin mem- 
branous lining of the shell remains intact. Kept in antiformin within 
this membrane the embryo may still be active at the end of 5 days, 
but if the membrane is burst by applying pressure the embryo is in- 
stantly killed by the antiformin. 
We have kept Ascaris swum eges containing vermiform embryos 
alive for several hours in carbolic acid, and embrvos were still active 
in eggs kept 5 weeks in crude petroleum and in petrolatum. In eggs 
kept 10 weeks in crude petroleum no living embryos were seen, and the 
shells of most of the eggs were collapsed, but in most of the eggs kept 
the same length of time in petrolatum the embryos were active and 
very few eggs with collapsed shells were observed. 
In view of the resistant nature and impermeability of the shell of 
the Ascaris egg it 1s evident that ordinary methods of disinfection 
by the application of chemical agents in more or less dilute solutions 
are of little or no use in preventing the spread of infection. Accord- 
ing, however, to results obtained by Wigdor (1918) and unpublished 
results of experiments by Dr. Raffensperger and Miss Cram, phenol 
solutions are destructive to the eggs of Ascaris (or Toxascaris in the 
case of Wigdor’s experiments), and it is possible that phenol disin- 
fectants may prove useful under some conditions in the control of 
Ascaris. 
AVENUE OF INFECTION WITH ASCARIS. 
Infection with Ascaris has been shown by repeated experiment to 
be the result of swallowing eggs containing fully developed embryos. 
_ The possibility of natural infection in other ways than by the swal- 
lowing of eggs, however, is not absolutely excluded. Martin (1913) 
injected eggs of Ascaris equorum containing active embryos beneath 
the skin of a guinea pig. When the animal was killed 41 days later 
many empty eggshells were found at the site of injection, showing 
that the eggs had hatched. The fate of the embryos was not deter- 
mined. Martin made similar experiments with the eggs of A. equo- 
rum and A. vitulorum on a dog, a rat, and guinea pigs, with similar - 
results. We have repeated Martin’s experiments, using eggs of 
A. suum containing active embryos (Experiment No. 13). 
Our experiments show that if introduced beneath the skin Ascaris 
eggs will hatch and that within a few days the larve will appear in 
