This paper deals with a method for obtaining living tissue from lymph nodes and tumors, and emphasizes the importance of studying living cells in pathologic processes. The results obtained from the study of abnormal lymph nodes by the application of these methods are discussed in a separate communication.1 Lymph nodes of patients usually are studied for diagnosis by ordinary pathologic technic after their surgical removal. Biopsy is not a procedure that can be repeated readily, and thus in following the development of disease processes, or the effect of therapy, it is not a satisfactory way of obtaining tissue for pathologic study. Furthermore, biopsy is refused by many patients, and is frequently difficult and at times impossible to perform with safety. Moreover, the usual technic for accurate diagnosis from the tissue obtained by biopsy requires several days. For these reasons material has been obtained from lymph nodes by puncture. This procedure