{'fraction_non_alphanumeric': 0.025757575757575757, 'fraction_numerical': 0.0, 'mean_word_length': 5.480392156862745, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Normal and heterotopic periosteum.

Normal periosteum is an osteoprogenitor cell-containing bone envelope, which can be activated to proliferate by trauma, retroviruses, tumors, and lymphocyte mitogens. Activated periosteum produces cartilage and bone, and is colonized by bone-resorbing cells. The osteogenic activity of periosteum is maintained in heterotopic sites and in vitro. Ectopic bone, however, is colonized by bone marrow precursor cells but does not develop a true periosteum. The absence of true periosteal envelope in the heterotopically induced bone may be the major, if not the only, difference between heterotopic and orthotopic bone deposits.