[155] That is to say so far as it is suffered to remain for any length of time in the vagina and comes more or less in contact with the atmospheric air; for in the case of healthy menstrual blood no injurious combination is set up at all or any foul acridity developed, as _John Stedman_ (Physiolog. Versuche und Beobachtungen,—Physiological Investigations and Observations, transl. from the English, Leipzig 1778. 8vo., pp. 50-54.) long ago maintained. It is more probable however that any slight putrefactive action occurring is in each case due not so much to this as to the _acid quality_ of the menstrual blood, which in conjunction with the acid vaginal mucus undergoes a kind of acetous fermentation in the vagina, the product of which has thus a corrosive effect. _Retzius_ indeed has lately not only found menstrual blood to possess an exceedingly acid reaction, but even proved that it contains free phosphoric and lactic acids. Comp. Arsberättelse om Svenska Läkare Sällskapets Arbeten, 1835., pp. 19-21. Froriep’s Notiz, Vol. 49., p. 237. [156] Hence too _Hugo Grotius_ writes (Commentar. ad Mosis lib. III.—Commentary on Book of Leviticus, ch. 15.): Sciendum est autem in Syria et locis vicinis non minus τὴν γονόῤῥοιαν quam τὰ ἐμμήνια habere aliquid contagione nocens, (But it is to be observed that in Syria and the neighbouring regions ἡ γονοῤῥοία (discharge from the genitals) no less than τὰ ἐμμήνια (menstrual discharge) contains a principle contagiously injurious). Even _Astruc_, the eager advocate of the American origin of Venereal disease, says (Vol. I. p. 92.): Sane constat in hac nostra Europa, quae magis temperata est, si cum menstruatis res habeatur, balanum et praeputium leviore phlogosi aut superficiariis pustulis, quae tamen brevi cessant, _plerumque_ affici. Quanto graviora ergo iis impendere credendum est, quos in calidiore et aestuante climate misceri cum foeminis non pudet, dum illis menses actu fluunt natura acerrimi et quasi virosi. Ideo forsan factum est, ut medici Arabes, qui regiones calidiores incolebant, quam Graeci et Latini, et primi et saepe disseruerint de pustulis et ulceribus virgae, oriundis ex coitu cum foeda muliere, hoc est (?), cum muliere menstruata. (It is an undoubted fact that in this Europe of ours, though enjoying a more temperate climate, if intercourse is had with women during menstruation, the _glans penis_ and prepuce are _generally_ attacked by some little inflammation or by superficial pustules, which however soon disappear. What much more serious consequences then must we suppose threaten those who in a warmer climate, one steaming with heat, are not ashamed to make coition with women, whilst their _menses_ are actually flowing, these being from the nature of the case exceedingly acrid and almost poisonous. Perhaps this is why the Arab physicians, who lived in warmer countries than the Greek and Latin practitioners, first and most often treated of pustules