I have more than once kept you informed of the inquiry concerning the effects of iodine on the human system, which has so long engaged the attention of several eminent chemists on the continent; and now have to report something further by M. Fourcault, whose communication thereupon to the Academie is entitled, 'On the Absence of Iodine in Water and Alimentary Substances, considered as Cause of Goitre and Cretinism, and on the Means of Preventing the Development of these Affections.' He has investigated the subject profoundly and analytically, and concludes that 'the absence or insufficiency of iodine in water and in alimentary substances, is to be considered as the primitive cause, special or _sui generis_, of goitre and Cretinism;' that the existence of the diseases does not depend on the presence more or less of sulphate of lime or magnesia in the animal economy; that 'iodine acts in goitre as iron in chlorosis--by restoring to the system one of its essential principles;' and that 'the most powerful secondary or auxiliary causes are: a coarse and uniform vegetable regimen; living at the bottom of deep, enclosed valleys; in low and damp houses, into which air and light penetrate with difficulty; the alliance of infected families among themselves; and the want of such employment as would yield a comfortable subsistence and proper development of the physical forces.' In commenting on these statements, Baron Thenard observed that M. Chatain, in the course of his able researches on iodine, had analysed the waters of those Alpine valleys most subject to goitre, and found that mineral almost entirely wanting. And it has been proved that sea-salt, containing a minute quantity of ioduret of potassium, acted as a preservative from goitre on all the inhabitants of a district who made use of it. The air, too, has been examined as well as the water, and, so far as yet ascertained, the proportion of iodine in the atmosphere is variable, and much greater in amount in some regions than in others. The activity prevailing in this particular branch of inquiry is the more encouraging, as the maladies which it aims at removing are of so peculiarly distressing a nature; and the investigation is one likely to lead also to valuable incidental results.