INFANCY AND CHILDHOOD. 1021 



secretion of the mother; by the dawn of the Intellectual powers, manifested 

 in the first efforts at speaking ; and by the acquirement of sufficient control 

 over the muscular apparatus, to render it subservient to the increasing desire 

 which then displays itself for independent Locomotion. All these advances 

 usually take place simultaneously, or nearly so, during some part of the 

 second year ; some Infants being much more forward than others, both in 

 " cutting their teeth " and in learning to walk and to talk. When they 

 have been completed, the Child enters upon a life which is in many respects 

 new. The alteration of its diet involves a much higher activity of all the 

 organs Which are concerned in making blood ; whilst its greatly increased 

 amount of exertion, both of body and mind, gives occasion to a more rapid 

 disintegration of the nervous and muscular tissues, and hence to a higher 

 activity of the Excretory organs. This will, of course, progressively aug- 

 ment, in proportion as the Nervo-muscular apparatus is brought, with ad- 

 vancing years, into more vigorous and more prolonged exercise ; until, with 

 the attainment of adult age, the disintegration of these tissues comes to be 

 the chief source of the Excrementitious products. But during the whole 

 period of increase, there is another source of demand for nutritive activity, 

 in that perpetual reconstruction of the fabric (involving a sort of continual 

 pulling down and rebuilding on a larger scale, all the old materials being 

 carried away as useless) which is a necessary condition of its growth : but 

 this demand of course slackens with the diminution of the rate of increase ; 

 aud at last it ceases altogether, just when the other attains its maximum. 

 Hence the demand for food, on the one hand, and the amount of excretory 

 matter set free from the body, on the other, are remarkably large during 

 the whole of this period : the child, as every one knows, consuming far more 

 nutriment than the adult, in proportion to the weight of their respective 

 bodies ; and the like being true of the quantity of carbonic acid exhaled 

 'from the lungs ( 311, in), and of the urea given oft' from the kidneys 

 ( 411). That the germinal capacity, though inferior to that of the embryo, 

 still persists in a high degree during the period of childhood and youth, is 

 shown in the readiness with which the effects of injuries and disease are re- 

 covered from ; for although the regeneration of lost parts does not take place 

 to nearly the same extent as during early embryonic life, yet up to a certain 

 point it is effected with great completeness, and with much greater rapidity 

 than at later epochs. It is still, in fact, rather in the exercise of formative 

 power, than in the production of nervo-muscular vigor, that the vital force 

 of the earlier part of this period is displayed ; and we may readily trace such 

 a relation of reciprocity between these two modes of its manifestations, as is 

 strongly indicative of the community of their source. For it is familiar to 

 every observer, that, when the growth of a child or a young person is pe- 

 culiarly quick, his nervo-muscular energy is usually feeble, and his power of 

 endurance brief, in comparison with that which can be put forth by one 

 whose frame is undergoing less rapid increase. And we observe, moreover, 

 that the capacity of resistance to depressing influences of various kinds, 

 which is a no less decided manifestation of the vital powers of the organism 

 (seeing that these influences are of such a kind as to tend towards its death), 

 is possessed by the latter in a far higher degree than by the former. This 

 is remarkably the case in regard to privation of food and depression of ex- 

 ternal temperature; under which, too, children and young persons succumb 

 much more speedily than adults. 



869. It is most interesting to trace, during the progress of the develop- 

 ment of the bodily fabric, the gradual expansion and invigoration of the 

 Mental powers. The acquirement of language constitutes the most ini- 



