entozoon

It is a semi-transparent entozoon; each segment is long compared to its breadth, and narrowed at both ends.

From Dogs and All about Them by Robert Leighton

An "entozoon" seems to the practical man a foolish, imaginary creature.

From Editorials from the Hearst Newspapers by Arthur Brisbane

When you know the entozoon you can dig him out and save the sheep's life.

From Editorials from the Hearst Newspapers by Arthur Brisbane

The entozoon of course gives rise to a variety of stale and melancholy jokes about the early bird, the worm that dieth not, and so forth.

From Two Trips to Gorilla Land and the Cataracts of the Congo Volume 2 by Sir Richard Francis Burton

But millions of sheep have been saved by the discovery that one of these fancy scientific entozoa, pressing on the brain, caused the sheep's death.

From Editorials from the Hearst Newspapers by Arthur Brisbane

The existence of entozoa, or parasitic animals, found in the interior of the bodies of other animals, and found nowhere else, is thought to support the same doctrine.

From A Theory of Creation: A Review of 'Vestiges of the Natural History of Creation' by Francis Bowen

We also know that similar entozoa in their wanderings in the tissues by accident of location, or by disease, or injury of their organs, not infrequently give rise to grave lesions in their hosts.

From West African studies by Mary Henrietta Kingsley

Perhaps the prevailing doctrine is in nothing placed in greater difficulties than it is with regard to the entozoa, or creatures which live within the bodies of others. 

From Vestiges of the Natural History of Creation by Robert Chambers

It spends its whole existence there, and is distinguished from other entozoa by having the mouth between two pores on each side, through which a spicular process comes out.

From A Treatise on Sheep: The Best Means for their Improvement, General Management, and the Treatment of their Diseases. by Ambrose Blacklock