A small proportion of sulphur is found in flesh and blood. We prove its presence in the egg by common experience. An egg--from which it escapes more easily than from flesh--discovers its presence by blackening silver, as every housekeeper knows, whose social position is too high for bone egg-spoons or too low for gold ones. This passion which sulphur entertains for silver is very strong, as every one knows who has ever been under that wholesome discipline which had its weekly recurrence at the delightful institution of Dotheboy's Hall; and what Anglo-Saxon ever grew up, innocent of that delectable vernal medicine to which we refer? Has he not found all the silver change in his pocket grow black, suggesting very unpleasant suspicions of bogus coin? The sulphur, being more than is wanted in the economy of the system, has made its escape through every pore in his skin, and, of course, fraternizes with the silver on its way. But it was of the sulphur which is natural to the body and always found there that we were speaking. When the animal dies, and the vital forces give way to chemical affinities, when the phosphorus and the rest take their departure, the sulphur, too, finds itself occupation in new fields of duty.
Chlorine and sodium, two more of the elements of animal structures, produce, in combination, common salt,--without which our food would be so insipid, that we have the best evidence of its being a necessary article of diet. The body has many uses for salt. It is found in the tears, as we are informed by poets, who talk of "briny drops" and "saut, saut tears"; though why there, unless to keep the lachrymal fluid from spoiling, in those persons who bottle up their tears for a long time, we cannot divine.
Perhaps we had better take the rest into consideration together,--the magnesia and iron, and whatever other elements are found in the body. Though some of them are there in minute quantities, the structure cannot exist without them,--and for their constant and sufficient supply our food must provide.
To see what becomes of all these materials after we have done with them, we must extend our inquiries among the articles of ordinary diet and ascertain from what sources we derive the several elements.