The method of parabiosis has been used extensively in the study of the humeral transmission of many substances and has been particularly useful in the study of the hormones controlling the reproductive tract and gonads. The method of parabiosis which has usually been used is that described by Sauerbruck and Heyde ('08). This method consists in uniting the skin and body cavities of the two animals (coelioanastomosis). We used the method of Sauerbruck and Heyde in a number of preliminary experiments which were designed to study the influence of oestrin on the gonad-stimulating complex of the anterior pituitary. The operations were all done with aseptic technique and reasonable post-operative care was taken of the animals. However, a large number of our animals died or the wounds became badly infected and in cases where the animals lived, the skin between the partners stretched and became twisted.(This particular disadvantage of the Sauerbruck and Heyde method is illustrated in Schmidt's paper ('22)). A study of the unsatisfactory results which we obtained using the method as described by Sauerbruck and Heyde convinced us that the infections and deaths were caused in most of the cases by the animals pulling on the sutures of the skin. We, therefore, concluded that the union between the animals must be made more substantial than can be done by skin and muscle union. Accordingly, the