tetanus antitoxin: antitoxin given for short-term immunization against tetanus in cases of possible exposure to the tetanus bacillus
thing: a separate and self-contained entity
myelomeningocele: a congenital defect of the central nervous system in which a sac containing part of the spinal cord and its meninges protrude through a gap in the vertebral column; frequently accompanied by hydrocephalus and mental retardation