538 The Philippine Journal of Science 1922 
DEPOSITION OF EGGS 
Letulle(21) says that the worms migrate to the smaller veins; 
on account of the larger size of the male, he is left behind, 
while the female continues her migration until she comes to 
a small vessel, which she blocks, causing stasis of the vessel. 
Attaching herself to the intima of the vessel she evacuates her 
ova, the spines of which, aided by the pressure of the blood, 
are enabled to pierce the walls of the vessels, and the whole 
mass of ova is forced into the perivascular tissue. 
Fairly(11) examined fresh pieces of bowel infected with 
Bilharzia hematobia [Schistosoma hematobium] and describes 
the process as follows: 
When the time for oviposition arrives the paired worms travel against 
the direction of the blood stream to the furthermost possible point. Hence 
the female leaves the male partner and being of a much narrower calibre, 
works her way into veins of small diameter, distending them in the process 
and only stopping when the mechanical resistance is too great for further 
progress. Here she deposits an ovum always in a characteristic fashion, 
the spine being directed posteriorly. The reason for this is that the ovum 
lies in a similar position in the uterus of the female. The female then 
slightly withdraws. Pari passu the distended vessel wall contracts down 
on the ovum. Again the female deposits an egg and withdraws, and 
again, the vessel wall contracts down on the foreign body. In Bilharzia 
hematobia infestation many eggs are deposited in this fashion, so that 
microscopically the venule, with its contained ova, presents the appearance 
of a string of sausages. Probably local vascular spasm is a big factor in 
the production of this picture. When the female finally withdraws from 
the branched venule the blood current, which has in the meantime been 
held up, assumes its normal course, driving the ova before it. The spines 
which point in the direction of the blood stream, and are in close apposition 
with the walls of the venule, naturally pierce the latter structure and are 
then, driven into the perivascular tissue. 
Whether the worms of Schistosoma japonicum are found in 
the venous or in the arterial side, it seems to me that the female 
worm, by blocking the smallest arteriole, or venule, causes an 
anemia. After depositing an egg or a mass of eggs she with- 
draws, and the blood rushes in and drives one or many ova 
through the wall of the vessel which has been weakened by 
the temporary anzmia and probably by the secretion of the 
contained miracidium or by some secretion from the mother 
discharged with the ova. In this way, the ova pass into the 
perivascular area. Once in the stroma of the intestinal mucosa, 
either the ova are expelled into the intestinal canal by the con= 
tractions of the intestinal wall or they cause necrosis and an 
inflammatory reaction; and, by the rupture of the small ab- 
