Although adipose tissue constitutes a large part of the total bulk of many of us (18 per cent by weight of a person of average nutrition, Voit) and is subject to many physiologic variations and pathologic alterations, nevertheless it has been the subject of relatively little study. In the leading text and reference books of pathology there is scarcely a mention of the adipose tissue as being possibly an actively functioning organ and a system subject to its own diseases. Because of this lack of consideration, adipose tissue presents many unsolved problems as well as many interesting phenomena, some of which will be reviewed in this presentation. Nearly thirty years ago the Chicago Pathological Society was privileged to have as a guest speaker that great pathologist and teacher of pathologists Prof. Hans Chiari,1of Prague, who spoke to us on "Die S[ill]bstständigkeit des Fettgewebes vom pathologischanatomischen Standpunkte." This cast a new light on the subject for me, and the interest aroused by his