442 OF NUTRITION. 



mere 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 in- 

 creased flow of blood towards a part is consequent upon, rather than a cause 

 of, an excess in its nutritive activity ; but still there are cases in which its 

 causative agency may be traced. Various examples of this have been sup- 

 plied 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 transplanted 

 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 its beak 

 to the ground ia feeding. So, again, it was remarked by Hunter, and has 

 been frequently 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 integuments 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 augmented afflux of blood which is determined 

 to the irritated surface. 1 



356. The greater number of cases of hypertrophy, however, must undoubt- 

 edly 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 remarkable example in the abnormal growth of an entire limb, or of 

 fingers or toes,' 2 which cannot with any probability be referred to an original 

 excess in the supply of blood, the enlargement of the arteries leading towards 

 such parts being almost certainly consequent upon their unusually rapid 

 growth, just as in the case of the uterine and mammary arteries of the preg- 

 nant female. The most remarkable instances of the acquirement of increased 

 formative activity, are presented to us in that augmented growth of the 

 nervous and muscular tissues, which is consequent upon the exercise of their 

 functional powers. This may be considered as, to a certain extent, a normal 

 adjustment of the supply to the demand ; but there are some instances in 

 which it takes place to such an extent as to become a positive disease. Thus 

 it not unfrequently happens that if young persons who naturally show pre- 

 cocity of intellect, are encouraged rather than checked in the use of the 

 brain, the increased nutrition of the organ (which grows faster than its bony 

 case) occasions pressure upon its vessels, it becomes indurated and inactive, 

 and fatuity and coma may supervene. Now although in such cases there 

 may probably have been some congenital tendency to preternatural activity 

 of the brain, which manifested itself in the precocity of intellect, yet there is 

 no doubt that this may be augmented by the " forcing system " of education ; 

 whilst on the other hand, it may be controlled by a system of management 

 adapted to the peculiar circumstances of the case. Excess of muscular de- 

 velopment is peculiarly prone to show itself in the involuntary muscles; but 



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



Congestion ; but this is not true hypertrophy ; lor thn bulk of tin- or^an is not aug- 

 mented by the increased production of its normal tissue, but by the addition of tissue 

 of an inferior type of organization, as in Inflammation. 



2 A case of hy|>erlro])hy of an entire limb was described by Dr. John Reid in the 

 Edinb. Monthly Journ., 1841], p. 198; and several cases of hypertrophy of the lin- 

 gers were described by Mr. Curling in the Mcd.-Chir. Trans., vol. xxviii. 



