Massachusetts has, by creating a Board of Health, and affording the same every facility for the prosecution of hygienic investigations of the greatest importance, laid the whole scientific world under a deep obligation. The reports issued have a very wide circulation, and embrace a variety of subjects, but second to none in interest and importance is the account of the experimental work carried out by the officials of the Board on the purification of water and sewage. These experiments have become classical, and have been conducted with a zeal and thoroughness which deserve the highest praise. It is in looking at the results achieved by the city of Lawrence in regard to its water-supply that some conception can be obtained of the immense importance to the community of the scientific experiments conducted in the State Laboratory. No expense has been spared, and for years past elaborate and costly experiments on a large scale have been carried out to determine the most efficient manner in which water may be rendered fit and safe for drinking. Now the death-rate in a community from typhoid fever may be taken as an index of the general sanitary conditions prevailing in such a community, the character of the public water-supply, not without justification, being regarded as a prime factor in its determination. One of the most significant points in the sanitary history of the State of Massachusetts is the almost uniform decline in the mortality from typhoid fever in proportion as measures have been taken to introduce better water-supplies and to improve those which already exist. Thus in the twenty years, from 1856 to 1876, the death-rate from this disease was 8·6 per 10,000 of population, whilst in the period from 1876 to 1895 it had fallen to 4·1 per 10,000, the improvement in respect of typhoid-mortality being coincident with the improvement made during the last twenty years in providing public water-supplies. In the words of one of the State reports, "The death-rate from typhoid fever has generally fallen as the per cent. of the population supplied with public water has risen, for the reason that the majority of the deaths from this disease have occurred among communities and portions of communities _not supplied with public water_." That this improvement is being maintained is seen from the fact that in the four-year period 1896-99 the deaths from typhoid fever in Massachusetts were further reduced to 2·6 per 10,000.