Analysis of information sources in references of the Wikipedia article "Bread and Roses" in English language version.
In this work, Galen does not specifically in one place state the quote mentioned by Edward Lane; however, in the first chapter of Natural Faculties he discusses the difference between plants and animals. Plants only have a physical body, while animals have both a physical body and soul. The body is fed by physical nutrients, such as bread, while the soul is fed by the senses. In this treatise, he studies the aspects of the physical body.
In any event, I am virtually certain that the song had been dormant for close on to 30 years until I came across sheet music for it while doing some research at the New York Public Library sometime in 1951. That's where the name Martha Coleman appeared. (This is just a guess, but I wouldn't be surprised if Martha Coleman turned out to be a pseudonym for Caroline Kohlsaat.) There is no evidence to indicate that this was particularly known as a song. The poem was somewhat known but not with a musical setting. The tune itself never caught on which is one reason why others have tried writing a new melody for it. I think if it was being sung prior to its publication in Sing Out! (January 1952), I would have known about it.
The quote comes via Arabic translation from the book Ḥalbet El-Kumeyt which was written by Shems-ed-deen Moḥammad En-Nowwájee († 1454) who attributes the quote to Galen. See pp. 167 (footnote 195), pp. 283
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