And now just a few personal remarks in conclusion. I have had much pleasure in giving to my old brother officers in these lectures the result of my experience in sanitary science. In doing so, I desired especially to impress on you who are just entering your profession the importance of giving effect to those principles of sanitary science which were left very much in abeyance until after the Crimean war. I have not desired to fetter you with dogmatic rules, but I have sought, by general illustrations, to show you the principles on which sanitary science rests. That science is embodied in the words, pure earth, pure air, pure water. In nature that purity is insured by increasing movement. Neither ought we to stagnate. In the application of these principles your goal of to-day should be your starting-post for to-morrow. If I have fulfilled my object, I shall have interested you sufficiently to induce some of you at least to seize and carry forward to a more advanced position the torch of sanitary science. * * * * * PASTEUR'S NEW METHOD OF ATTENUATION. The view that vaccinia is attenuated variola is well known, and has been extensively adopted by English physicians. If the opinion means anything, it signifies that the two diseases are in essence one and the same, differing only in degree. M. Pasteur has recently found that by passing the bacillus of "rouget" of pigs through rabbits, he can effect a considerable attenuation of the "rouget" virus. He has shown that rabbits inoculated with the bacillus of rouget become very ill and die, but if the inoculations be carried through a series of rabbits, a notable modification results in the bacillus. As regards the rabbits themselves, no favorable change occurs--they are all made very ill, or die. But if inoculation be made on pigs from those rabbits, at the end of the series it is found that the pigs have the disease in a mild form, and, moreover, that they enjoy immunity from further attacks of "rouget." This simply means that the rabbits have effected, or the bacillus has undergone while in them, an attenuation of virulence. So the pigs may be "vaccinated" with the modified virus, have the disease in a mild form, and thereafter be protected from the disease. The analogy between this process and the accepted view of vaccinia is very close. The variolous virus is believed to pass through the cow, and there to become attenuated, so that inoculations from the cow-pox no longer produce variola in the human subject, but cow-pox (vaccinia). As an allied process, though of very different result, mention may be made of some collateral experiments of Pasteur, also performed recently. Briefly, it has been discovered that the bacillus of the "rouget" of pigs undergoes an increase of virulence by being cultivated through a series of pigeons. Inoculations from the last of the series of pigeons give rise to a most intense form of the disease.