facilities were initially “severely limited by the lack of special wards or buildings where such cases could be isolated”. (Godias and Lowell 1952) The lack of adequate facilities was only exacerbated by the conditions in which people lived within the city. Tuberculosis was commonly associated with dirty, poorly lit conditions, and a significant group of the population lived in homes characterized by dark, poorly ventilated environments. areas. Daniel Freund, provides an example of these conditions using an image by Jacob Riis entitled “Baby in slum tenement, dark Stairs –its Playground”. (Freund 2012). The title of the image is self-explanatory and the idea is clear: the darkness and dirty conditions bred disease and contributed to the spread of tuberculosis. These conditions were addressed through changes to the building code outlined by the Tenement Act of 1901. Daniel Freund notes that the act resulted in the terraced structure of buildings that allowed greater infiltration of light into the city below. The impact has been used to redesign new residential buildings to dramatically increase exposure to sunlight. (Freund 2012) The design is still evident today in the designs of the Chrysler Building and the Empire State Building, and the push for light became central to the reduction of disease in the city. Heliotherapy became important in this period because it was used in the treatment of tuberculosis. New research had shown that ultraviolet light, contained in the solar spectrum, had antibacterial properties. Dr. Woloshyn notes that physicians of the time were aware of various published experiments conducted by Louis Pasteur, Arthur Downes, and Robert Koch that demonstrated antimicrobial characteristics… half of article… Tuberculosis in New York 1900-1950. Grasso, H.L. (1922). "Heliotherapy in tuberculosis". New York Journal Of Medicine 281-282.Howson, C. R. (1928). "Heliotherapy in pulmonary tuberculosis: its possibilities and its dangers". Cal West Med 29(1): 25-30.Kuzma, M. (2014). "Friends of JN Adam." Retrieved from: http://jnadam.org/,3/23/14Langdon, B. (1930). "The limitations of heliotherapy in pulmonary tuberculosis". Annals of Internal Medicine 4(4): 376-378.Sykes, R. (2001). "Penicillin: from discovery to product." Bulletin of the World Health Organization 79(8): 778-779.Waldmann (2014) Waldmann Engineer of Light: Light Sources For Phototherapy. WaldmannWoloshyn, D.T. (2011) Our friend, the sun: images of light therapies from the Osler Library collection c.1901-1944. Source from McGill University: http://www.mcgill.ca/files/_nea/170546_ourfriendsun.pdf