instruction: provide the number of patients categorized under chemistry lab test who have been diagnosed with contusion of face, scalp, and neck except eye(s).
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE diagnoses.short_title = "Contusion face/scalp/nck" AND lab."CATEGORY" = "Chemistry"