420 OF NUTRITION. 



capacity has undergone a gradual diminution, whilst the exercise of the 

 animal powers has become vastly increased, the formative processes are only 

 capable of maintaining the Organism in its state of completeness and vigor, 

 by making good the losses consequent upon the continual disintegration to 

 which it is subjected by its nervo-muscular activity. And with the advance 

 of years, the further diminution of the productive 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 power of action. (See chap. xx. ) 



336. 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 ad- 

 vance 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 displayed in the 

 continuous renewal of those minor peculiarities which constitute the char- 

 acteristic features of the individual, and which serve to distinguish him from 

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

 ally derived from the germ, is evident from this, that a similar moulding (so 

 to speak) of the nutritive material takes place, in its original development, 

 at first 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 re- 

 marked, the tissue of a cicatrix grows and assimilates nutrient material, ex- 

 actly 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 fore- 

 finger 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 

 of the part; and this is stronger the more frequently it recurs, until at last 

 it becomes inveterately established. There is, however, in the Tissues gener- 

 ally, as in the Blood, 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 

 typical structure of parts generally restored, when the morbid tendency has 

 been overcome; and that even cicatrices and indurations, notwithstanding 



shows that these intervals arc entirely regulated by temperature; for if one of the 

 ordinary deciduous trees of temperate climates he transferred to a tropical climatr, it 

 will live mueh faster, its leaves being shed far more frequently, and being replaced 

 much more spi-i>dily ; so that two, or even three, successive exuviations and reproduc- 

 tions of its foliage may take place within a year. 



