HYPERTROPHY. 555 



intermittent activity of the sexual apparatus of the finale affords a remarkable 

 example of the same principle ; this being marked not merely in the enormous 

 development of the uterus and mammary glands, as a consequence of conception, 

 but in the periodical change which takes place in the ovaries, whereby the ova 

 are matured and thrown off at certain regular intervals. The decline in the 

 formative power of these same organs, moreover, when as yet the organism in 

 general shows but little indication of deterioration, is another characteristic 

 example of the variation in Nutritive activity resulting from the inherent en- 

 dowments of the part, and essentially irrespective of the condition of the blood, 

 of the circulation, and of the organism as a whole ; but, as formerly shown 

 ( 203), the production and maintenance of other and apparently unconnected 

 organs are complementalty dependent upon the formative activity of the genera- 

 tive apparatus. 



596. The abnormal excess of Nutritive change which properly constitutes 

 Hypertrophy, appears to depend upon a departure from one or other of the con- 

 ditions, under which, as already specified, the change normally takes place ; 

 namely, the right composition of the blood, a due supply of such blood, and a 

 proper formative capacity in the part itself. Of the excess of nutrition result- 

 ing from the presence of an excess of the peculiar materials of certain tissues in 

 the circulating fluid, examples have already been given ( 120) ; it is important 

 to remark, however, that, although hypertrophy may be thus induced in any of 

 the tissues which constitute the instruments of organic life, yet there is no evi- 

 dence that either the nervous or the muscular apparatus can be forced (so to 

 speak) to an augmentation in bulk by the abundance of their nutritive materials. 

 With regard, in the next place, to the supply of blood, there can be no doubt 

 that in general an increased flow of blood towards a part is consequent upon, 

 rather than a cause of, an excess in its nutritive activity j but still, there are 

 cases in which its causative agency may be traced. Various examples of this 

 have been supplied by the experiments and observations of John Hunter, the 

 records of which are left in his Museum. Thus, if the spur of a cock be trans- 

 planted from the leg to the comb, which is a part far more vascular than that 

 with which it was originally connected, it undergoes an extraordinary augmenta- 

 tion in size ; having in one instance grown in a spiral form, until it was six 

 inches long ; and in another curved forwards and downwards like a horn, so 

 that its end needed to be often cut, to enable the bird to bring his beak to the 

 ground in feeding. So, again, it was remarked by Hunter, and has been fre- 

 quently observed since, that an increased growth of hair often takes place on 

 surfaces to which there is an increased determination of blood as a consequence 

 of inflammation in some neighboring part, though not from the surface of the 

 inflamed part itself. So it sometimes happens that when an ulcer of the integu- 

 ments of the leg has long existed in a young person, the subjacent bone may 

 share in the increased afflux of blood, and may enlarge and elongate. And it 

 seems not improbable that we are to attribute the increased thickness of the 

 cuticle on parts which are exposed to continual pressure or friction, to the aug- 

 mented afflux of blood which is determined to the irritated surface ( 241). * 

 The greater number of cases of Hypertrophy, however, must undoubtedly be 

 referred to the preternatural formative capacity of the part itself ; and this may 

 either be congenital or acquired. Of this congenital excess, we have a remark- 

 able example in the abnormal growth of an entire limb, or of fingers or toes, 2 

 > 



1 It is commonly said that local hypertrophy may be induced by long-continued Conges- 

 tion; but this is not true hypertrophy ; for the bulk of the organ is not augmented by the 

 increased production of its normal tissue, but by the addition of tissue of an inferior type of 

 organization, as in Inflammation ($ 609). 



2 A case of hypertrophy of an entire limb was described by Dr. John Jleid in the 

 "Edinb. Monthly Journ.," 1843, p. 198; and several cases of hypertrophy of the fingers 

 were described by Mr. Curling in the " Med.-Chir. Trans.," vol. xxviii. 



