The term “supplies, materials and equipment” as used in this Division shall include any and all articles or things which shall be furnished to or used by any Office, department, institution or agency of the county government, including supplies necessary for dieting prisoners confined in the jail of said county. “Contractual services” shall include all purchases, leases, and contracts for impersonal services, necessary for the operation of any Office, department, institution or agency of the county government which are not encompassed in the above definition of “supplies, material and equipment”.