FORMATIVE POWER OF INDIVIDUAL PARTS. 551 



adult condition, the germinal capacity has undergone a gradual diminution, 

 whilst the exercise of the animal powers has become vastly increased, the forma- 

 tive processes are only capable of maintaining the organism in its state of com- 

 pleteness and vigor, by making good the losses consequent upon the continual 

 disintegration to which it is subjected by its nervo-muscular activity ( 132). 

 And with the advance of years, the further diminution of the reproductive 

 capacity involves, on the one hand, a progressive decrease in the substance of 

 the tissues and organs most important to life (their bulk, however, frequently 

 remaining unchanged, or even increasing, in consequence of the accumulation 

 of fat), and on the other, a gradual weakening of its powers of action ( 133). 

 591. The performance of the function of Nutrition, the demand for which 

 arises out of the causes that have been now discussed, is dependent, not merely 

 upon a due supply of pure and well-elaborated blood, but also upon the normal 

 condition of the part to be nourished, and especially upon its possession of a 

 right measure of " formative capacity " in virtue of which, the newly produced 

 tissues are generated in the likeness, as well as in the place, of those which have 

 become effete. The exactness of this replacement is most remarkably shown in 

 the retention of the characteristic form and structure of each separate organ or 

 part of the body, and thus of the entire organism, through a long series of years ; 

 no changes being apparent (so long as the state of health is preserved), but such 

 as are conformable to the general type of that alteration which the organism 

 undergoes with the advance of life. And not only is this to be noticed in the 

 conservation of all those distinguishing points of structure which mark the 

 species, and are essential to its well-being ; but it is still more remarkably dis- 

 played in the continuous renewal of those minor peculiarities, which constitute 

 the characteristic features of the individual, and which serve to distinguish him 

 from his fellows. And how much this depends upon the formative capacity 

 originally derived from the germ, is evident from this, that a similar moulding 

 (so to speak) of the nutritive material takes place, in the first instance, into the 

 form characteristic of the species, and afterwards into that which marks the 

 individual, and that the peculiarities of the individual are frequently such as 

 have been distinctive of one or other of the parents, or present a combination of 

 both. But it is curious that the formative power should often be exercised, not 

 only in maintaining the original type, but also in keeping up some acquired 

 peculiarity; as, for example, in the perpetuation of a cicatrix left after the 

 healing of a wound. For, as Mr. Paget has remarked, the tissue of a cicatrix 

 grows and assimilates nutrient material, exactly as do its healthy neighboring 

 tissues ; so that a scar which a child might have said to be as long as his own 

 forefinger, will still be as long as his forefinger when he becomes a man. And 

 when the mode of nutrition in any part has been altered by disease, there is 

 frequently an obstinate tendency to the perpetuation of the same alteration ; or, if 

 the healthy action be for a time restored, there is a peculiar tendency to the renewal 

 of the morbid process in the part ; and this is stronger the more frequently it 

 recurs, until at last it becomes inveterately established. There is, however, in the 

 tissues generally, as in the blood ( 207), a general tendency to a return to the 

 normal type, after it has undergone a temporary perversion ; and thus it is that we 

 find the normal structure of parts gradually restored, when the morbid tendency 

 has been overcome; and that even cicatrices and indurations, notwithstanding their 

 usual obstinate persistence, occasionally disappear. The normal type is, perhaps, 

 less likely to be thus recovered, when the departure from it is very slight, and 



its leaves being shed far more frequently, and being replaced much more speedily ; so that 

 two, or even three, successive exuviations and reproductions of its foliage may take place 

 "within a year. 



