Dr. Stevens gives various illustrations, out of primitive customs, and in the experience of modern practitioners, of curative and prophylactic uses of salt in the treatment of fevers, where the condition of the blood seems to be a main source of evil. Aside from the question whether the claims of Dr. Stevens have been substantiated by later researches and experiments, his investigations and assertions are of interest as showing that, in the realm of modern science as of primitive practices, salt and blood have seemed to many to have interchangeable values. If, indeed, this theory of Dr. Stevens, elaborated so carefully in the first third of the nineteenth century, in which he claims that salt practically represents blood, stood all by itself in the history of medicine, it would have less importance than it has in a formal treatise of this kind; yet even then it would show that such an idea had before now found a place in the human mind. But it by no means stands thus alone; a similar claim has been made both earlier and later. Pliny, in his day, at the beginning of the Christian era, records it as the common belief that salt is foremost among human remedies for disease, and among preventives of sickness of all kinds.[47] He gives prominence to salt as a cure of leprosy,[48] whereas blood transfusion and blood bathing was the traditional treatment of that disorder.[49] Pliny also speaks of salt itself, and of salt fish in large quantities, as a supposed remedy for the bite of serpents,[50] this being in the line of asserted remedies among the Indians, according to Dr. Stevens. Various other disorders, especially of the blood, are named by Pliny as curable by salt. [47] _Hist. Nat._, XXXI., 45. [48] _Ibid._ [49] _Blood Covenant_, pp. 116 f., 125, 287 f., 324. [50] _Hist. Nat._, XXXI., 41; XXXII., 17. Seventy years after the treatise of Dr. Stevens, a volume, recently published in London by C. Godfrey Gümpel on "Common Salt,"[51] claims even more than Pliny, or any writer since his day, for "the vital importance of common salt for our whole physical and social life." He claims that of all the constituents of our life's blood "there is none which can possibly surpass common salt in its necessity for a strong healthy blood,"[52] and that both the red corpuscles and the white are largely dependent for their normal condition on "the presence of common salt in the system."[53] [51] _Common Salt: Its Use and Necessity for the Maintenance of Health and the Prevention of Disease_, p. 1. [52] _Ibid._, p. 37. [53] _Ibid._, p. 41.