Rufus Wheeler Peckham, United States v. Laws — Opinion of the Court
“ It is not the fact that the chemist keeps his services open for employment by the public generally which is the criterion by which to determine whether or not he still belongs to, or is practicing, a recognized profession. So long as he is engaged in the practical application of his knowledge of the science, as a vocation, it is not important whether he holds himself out as ready to make that application in behalf of all persons who desire it, or that he contracts to do it for some particular employer, and at some named place. ”
