Its _course_ is always in a certain sense progressive. Occasionally it appears to keep pace throughout with the general growth of the body, but nearly always the abnormal growth strides in advance, sooner or later, so that the disproportion of the affected part to the rest of the body becomes more and more pronounced. Its progress may be uniform and continuous, or terms of slow increase or apparent arrest may alternate with a new and rapid development. In some instances the process does not extend beyond the primary limits, while in others it may spread centripetally, and often at a very rapid rate, as in v. Fischer’s case (_l.c._), in which amputation of an hypertrophied finger was followed within a few months by hypertrophy of the whole limb. In two cases reported by Mr. F. S. Eve[33] a growth became disproportionally active at the ages of twenty-three and thirty-seven respectively. Similar instances have been published by Wittelshöfer, and the author (_l.c._). The addition of new tissue goes on, as a rule, without pain, inflammation, or interference with function; but in a case of von Fischer’s, burning pain was associated with trophic ulceration; and Friedberg’s patient,[34] who appeared to be the subject of an associated elephantiasis Arabum, had symptoms that somewhat resembled the inflammation crises of elephantiasis. In the majority of cases the _functional power_ of the enlarged part is not augmented, but true unilateral hypertrophy, _i.e._, increased tissue hypertrophy with proportionally increased functional activity, is sometimes found. The cases described long since in general terms by Geoffroy St. Hilaire,[35] as marked by an unequal development of the two sides of the body in one or more regions, were probably of this nature, and those of Ollier, Finlayson, and Langlet, may also claim a place in the same class. In Ollier’s case[36] the face, thorax, abdomen, and both extremities of one side, were uniformly larger than the corresponding parts of the opposite half of the body, the vascularity of the hypertrophied side was increased, the temperature elevated, and the limbs were more powerful. There were no nævoid growths, and it is noteworthy that in association with an absence of evident abnormality of thoracic, pelvic, and abdominal viscera, the mammary glands preserved their symmetry. The cases of Devouges, Adams, and Finlayson, also presented certain points of resemblance to true hypertrophy. In the first the whole of one side was hypertrophied, except perhaps the abdominal wall, where nothing unusual was noticed. The details are very imperfect, but according to the patient’s statement, the strength of the arm on the hypertrophied side was greatly in excess of that of its fellow. In Adams’s case the giant growth of the right lower extremity was apparently uniform, and the femoral and all other accessible arteries were considerably enlarged, but nothing is said as to muscular power. In