35 U.S. Code § 114 - Models, specimens
The Director may require the applicant to furnish a model of convenient size to exhibit advantageously the several parts of his invention.
When the invention relates to a composition of matter, the Director may require the applicant to furnish specimens or ingredients for the purpose of inspection or experiment.
Based on Title 35, U.S.C., 1946 ed., § 34, part (R.S. 4890 and 4891).
The change in language in the second paragraph broadens the requirement for specimens.