PD is a progressive neurodegenerative disorder which includes motor and non-motor (autonomic) symptoms, such as constipation. OMM has been shown to improve constipation symptoms in non-diseased subjects and cerebral palsy subjects. Constipation will be measured before, during, and after treatment by a constipation scoring system (Cleveland Criteria) to measure the severity of constipation and by the Bristol Stool Scale to measure colonic transit time. The study subjects' assessment of their constipation symptoms (PAC-SYM) and quality of life (PAC-QOL) will also be measured throughout the study.