If we except the microbes already referred to, parasites in the bladder are of secondary importance. The echino-coccus may burst into the pelvis of the kidney, and portions of the parasite pass into the bladder. Ascarides and oxyurides have been found to wander into the bladder. The distoma haematobium, by the penetration of its ova, produces considerable irritation and haemorrhage.

Sarcinae have been found in the urine in cases of inflammation of the bladder, but rarely.