Preface

then my chief, suggested that I should try to investigate the difference in vitainin D demands between breast-fed and bottlefed infants. I decided Lo study this question in premature infants and began by coinparing pairs of twins of which the one was fed human milk and the other cow's milk, but no vitamin D. Surprisingly enough, the twin who had had human milk in almost all cases showed iiiore abnormal values for serum phosphatasc and serum inorganic phosphorus, than i h e one who had had cow's milk, and also in some cases rontgcn signs of rickets, while the cow's inilk twin showed nornial riintgen findings. These observations gave rise to this investigation. Professor Wallgren has been most interested in m y work all the time, and facilitated it in every way. His help and encouragement have been of the greatest importance to me, and I am most grateful to him for this. The chemical analyses have a11 been carried out at the Central Laboratory of Sahlgren's Hospital. To Professor Jiirfpn L e h izzcrnn, chief of' the Laboratory, I am much indehted for thv hospitality and interest lie has shown me during these years and for his readiness to discuss the different problems which have suggesled thenisclvcs during the work and which have 011 inany points decided the course of the investigation. The chief riintgenologist of Sahlgren's Hospital. Mcd Doctor (;ostn Rzznstronz, has earned m y warm thanks for the numerous riintgen pictures and for his willingness to arrange the riint:g:eu examinations in the best way for the premature infants. Thc. chief riintgenologist of the (:hildren's Hospital in Giiteborg, 1)r. Carl Johcrn Hmzsson, and the riinlgenologist of the Norrtull Hospital in Sfockholm, I)r. 0lioer Axe'n, have both examined all the riintgen pictures. I am most gratelul to them for their iiitercsted work in this niatter.