This slide shows a section of skeletal muscle the containing encysted larvae of the nematode parasite Trichinella spiralis.  Humans can contract the parasite by eating raw or inadequately cooked pork or bear meat.  Once ingested, enzymes in the digestive system trigger the release of the encysted worms, which mature, mate and produce offspring.  These juvenile worms then enter the host's lymphatic system and are distributed through the body via the circulatory system to active skeletal muscle into which they burrow and become enclosed in cysts.