ROUNDWORM ASCARIS LUMBRICOIDES—SCHWARTZ A479 
precedes their later development in the small intestine, has given 
rise to considerable speculation. It is certain that there is much 
in the developmental history of this helminth that, on the surface, 
at least, appears to some investigators seemingly superfluous and 
difficult to explain. The exit of the larvae from, and their subsequent 
return to, the intestine, partly by passive movement with the blood- 
stream, and partly by their independent movements, have been re- 
garded by some helminthologists, especially by Fiilleborn (4, 5), as 
a probable recapitulation of the evolutionary history of these worms. 
Fortunately, however, the discoveries pertaining to the life cycle of 
Ascaris have opened up, in addition to these interesting speculations, 
new vistas so far as concerns the immunology of this worm infec- 
tion. Possibly one of these is the host’s vigorous defense reaction 
following the penetration of the larvae into abdominal and thoracic 
organs. This defense reaction might be responsible for the difficulties 
that so many investigators have experienced in attempting to rear 
these helminths from the embryonated egg to the adult worm in the 
natural hosts. Evidently, not all the problems relating to Ascaris 
infection have been entirely solved. What has been uncovered in 
recent years has opened the door a little wider, so as to permit 
_ further exploration of what still remains undisclosed. 
BIBLIOGRAPHY 
1. DAVAINE, C. 
1859. Recherches sur le développement et la propagation du trichocéphale 
de V’homme et de l’ascaride lombricoide. Journ. Physiol. Homme, 
Paris, vol. 2, pp. 295-200. April. 
1863. Nouvelles recherches sur le développement et la propagation de 
Vascaride lombricoide et du trichocéphale de ’homme. Compt. 
Rend. Soc. Biol., Paris (1862), ser. 3, vol. 4, Mém., pp. 261-265. 
3. EPsTEIN, ALOIS. 
1892. Ueber die Uebertragung des menschlichen Spulwurms (Ascaris lum- 
bricoides). Verh. Versam. Ges. Kind. Deutsch. Naturf. u. Aertze, 
Wiesbaden (1891), vol. 9, pp. 1-16. 
4. FULLERBORN, F. 
1922. Ueber den Infektionsweg bei Ascaris. Klin. Wochenschr., vol. 1, No. 
20, pp. 984-988. 
5. 
1927. Ueber das Verhalten der Larven von Strongyloides stercoralis, 
Hakenwitirmern und Ascaris lwmbricoides im Kérper des Wirtes 
und ein Versuch, es biologisch zu deuten. Beihefte 2, Arch. 
Schiffs.- u. Tropen-Hysg., vol. 31, pp. 151-202. 
6. Grassi, G. 
1887. Trichocephalus und Ascaris-Entwicklung. Preliminarnote. 
Centralbl. Bakt. u. Parasit., Jena, vol. 1, No. 5, pp. 131-132. 
Ue * ° 
1888. Weiteres zur Frage der Ascaris-Entwicklung. Centralbl. Bakt. u. 
Parasit., Jena, vol. 3, No. 24, pp. 748-749. 
