It is a very singular fact, that the medical profession in India, the birthplace and home of the cholera, almost universally reject the doctrine of contagion. If those most observant and familiar with its history, its prevalence, and its annual recurrence as an endemic disease, which they are called to treat in all its varied phases, have discovered no contagious character by which it can be propagated, it may be safely inferred that it is not contagious in the common acceptation of the term, and that its extension over the earth is governed by some other principle, and that the predisposing and localized causes which are always in operation in India exercise no small share in its diffusion, in directing its course, aggravating its severity, increasing or diminishing its fatality, and determining the duration of its prevalence in particular localities. When its infecting germs have gained a lodgment in any city, section, or country, they may be stimulated and become exceedingly active in the production of the disease through these influences. As to its introduction into different countries, it is quite evident that the germ, or latent principle of the cholera-poison, exists in such a state as to be capable of transportation, and may in this way be diffused to almost any extent when the localizing influences are sufficient to develop its energies. In this, as in all other zymotic diseases, some persons are more susceptible of an impression and more liable to an attack than others. Though no class can be considered exempt, yet there are some whose organization, or innate protective principle, seems to render them impervious to its influence. The cholera, however, is no respecter of persons, or rank, or condition. The anæmic and cowardly in all ranks and conditions are peculiarly liable, and are the most defenceless and unresisting when invaded. In Europe, the probable numbers attacked in that part of the world appear from statistics to be, in France, as 1 in 300; Russia, as 1 in 20; Austria, as 1 in 30; Poland, as 1 in 32; Holland, as 1 in 144; Germany, as 1 in 700. "The circumstance of one attack by no means protected the individual from a second in the same, or any subsequent year; still a repetition of the disease in the same person in the same year was rare." CHAPTER II. SECTION I.--PATHOLOGY. The doctrine now universally accepted and prevailing regarding its Pathology is, that a poison, virulent, subtle, and unknown, has been absorbed, and primarily infects the blood, so that, after a longer or a shorter time, a primary disease of this vital fluid is produced, and that the poison undergoes an enormous process of multiplication in the living body of the cholera patient, as the direct result of this morbific process so established, and that changes are induced in the function of respiration directly consequent on this alteration of the blood.