Low radioactive barium is swallowed as contrast medium for the X-ray film. The contrast medium (barium) here shows the small bowel. The worms are the black lines within the contrast. In this case they are all arranged tidily in the long axis of the bowel. This might be the reason why they do not cause any obstruction despite such large numbers.

Long axis means that the worms are all lined up facing the same way...up the bowel, not across it. If some worms were lying crossways and some lying in the long axis and others just lying higgledy-piggledy then they would form what we call a "bolus" and that is the basis for bowel obstruction by ascaris. If they all line up like soldiers on parade then food can pass between them or around them and no obstruction occurs.

The "Barium meal" is an X-ray technique where the patient swallows a metallic-based fluid (Barium is the metal) which shows up as white on an X-ray film. The radiologist can watch what happens as this fluid is swallowed and as it goes on down through the stomach and small intestine.

Photo by Larry Hadley, South Africa