142 PARASITOLOGY. 
constantly taking the sulphate of iron into the 
intestinal tract it will create an unfavorable place for 
the development and life of the worm. 
MA-COLUMBIANUM (Columbia). 
Synonym.—Oesophagostome of Columbia. 
Distribution.—Found commonly in the United 
States. First discovered in the District of Columbia. 
Description.—The worm is thread- 
like in calibre, white in color, slightly 
tapering anteriorly; the mouth is circu- 
b lar and provided with a double row of 
\ teeth arranged in a crown-like form; 
Fig. 52— the caudal pouch of the male is saucer- 
OESOPHAGOSTOMA shaped; the tail of the female termin- 
CoLUMBIANUM eB a 
a, Male. ates in a rather sharp point; the male 
b, Female. measures about three fourths of an 
inchin length, the female about oneinch. 
Lite Cycle.—The ovigerous female lays its eggs in 
the intestinal tract, which find their way to the ex- 
ternal world with the feces; the embryos are taken 
up by the host through the contaminated food and 
water; upon reaching the intestinal tract they pene- 
trate the mucous membrane and produce nodules 
which are irregular in outline and vary in size up to 
a pea; these nodules are found in both small and 
large intestines; often in badly infested cases em- 
bryos are noted to invade the mesentery and mes- 
enteric lymph glands and liver. The tumor, smaller 
in size than a pin-head, contains a cyst in which is 
found a growing embryo coiled in a ring-like shape, 
fioating in a colorless fluid; in the second stage the 
embryo is still in the cyst but a small quantity of 
