By an Act passed in 1844, it was declared absolutely illegal, on the expiration of thirty years after the passing of the Act, to carry on certain noxious businesses in any premises nearer a dwelling-house than 50 feet, or nearer a public way than 40 feet--the business of slaughtering being among the number. Until 1851 there was no control over slaughter-houses; any one could conduct a slaughter-house who pleased, subject only to the common law as to doing anything which might be considered a nuisance.[128] The Metropolitan Market Act, passed in that year, required that all slaughter-houses should be licensed by the justices, thus establishing some form of control over them. When, in 1874, the expiration of the thirty years drew nigh, doubts were raised by those interested in their continuance as to the interpretation of the Act of 1844. The Select Committee, which was investigating the subject of "Noxious Businesses," stated that no evidence had been given before it to show that any of these trades when properly conducted affect the health of the persons living near the premises, and Parliament, accepting this view, passed an Act which undid the enactment of 1844, and allowed slaughter-houses to be continued indefinitely under license. At the same time it conferred on the central authority, the Metropolitan Board of Works, power to make bye-laws with respect to certain noxious trades. And so this fertile cause of insanitation--slaughter-houses--was perpetuated to the present time. There was, however, a far more general and potent cause of disease and death, and general detriment to the public health, than the pollution of the atmosphere by noxious trades, and that was the reckless scattering abroad of infectious or contagious diseases by persons afflicted with or in contact with such diseases. The Metropolitan Asylums Board had already erected hospitals, and were doing a vast amount of good and preventing the spread of disease. But by the people themselves the seeds of infection were scattered broadcast. Dr. Simon, the Medical Officer to the Privy Council, in his Report of 1865, wrote:-- "As to contagions already current in the country, practically any diseased person scatters his infection broadcast, almost where he will--typhus or scarlatina, typhoid or smallpox, or diphtheria, ... the present unlimited license seems urgently to demand restriction." But the license to kill remained without restriction, except that of entering a public conveyance.[129] As the Medical Officer of Health for St. Mary, Newington, wrote in 1871:-- "How many are the ways in which the spread of contagious disease is, as it were, invited, no one knows better than a sanitary officer. Washing, mangling, needlework, go on in many an infected house; children, aye adults also, the sick and the sound, mix indiscriminately. I have even known the exhibition, as a sight, of the corpse of a smallpox patient...."