These are usually Sacs containing hair, skin, muscle, bone, or other natural tissues, and only exceptionally do they show the distinct outline of the animal.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
Here is a part of the body difficult to get at, and as a consequence of bad diet and unwholesome ways of living, infections will start there, and pus Sacs be formed, and the poisons absorbed into the blood-stream and distributed through the body.
"The Book of Life: Vol. I Mind and Body; Vol. II Love and Society"
Upton Sinclair
The cells, or cavities, that line the air passages and air Sacs at the ends of the bronchial tubes.
"A Handbook of Health"
Woods Hutchinson