ALTHOUGH it has been known for more than 70 years and frequently demonstrated during that time that lymphatic vessels proliferate in inflammation and repair, the fact has not yet received general recognition. Those methods of observation which give us knowledge concerning the part played by blood vessels do not yield any certain information about the behaviour and reactions of lymphatics. Unless filled with some opaque or coloured material the finer ramifications of these vessels are invisible during life nor can they be identified with any degree of certainty in sections. The injection method for showing up lymphatics has been used for many years for anatomical purposes, but it has not eome into general use as an every-day technique for pathological investigations. Probably it is for these reasons that lymphatic vessel reactions have received scant attention in the text-books of pathology, a fact recently pointed out by Sampson (1936). The evidence in favour of the occurrenee of regeneration and proliferation of lymphatic endothelium based on growth in human granulation tissue and on experiments made by Vecchi (1911) was accepted by Winkler (1924). In a, more recent review of the subject, however, this author (1934) expressed the opinion that, in spite of numerous experiments on animals, satisfactory evidence of ability to regenerate had not yet been obtained. No reference was made to American work. Hellman (1930) was of the opinion that growth and branching of lymphatics could occur in adult life by budding. Ackernecht and Krause (1929) state that little is as yet known on the subject of regeneration of lymph capillaries.