The author stated that when he commenced these experiments, in 1832, his object was to ascertain, first, what effect different diseases had on the constitution of the blood; and, secondly, what effect various therapeutic agents had on that fluid in a state of health and of disease. As the experiments of Andral and others, published since these experiments were commenced, had done much to elucidate many points of the first subject of inquiry, the author limited this communication to a small portion of the latter inquiry.