688 DEVELOPMENT OF THE BODY AFTER BIRTH. 



seems to be accomplished, during this period, to a considerable 

 extent through the skin, which is remarkably soft, vascular, and 

 ruddy in color. The animal heat is also less actively generated 

 than in the adult, and requires to be sustained by careful protec- 

 tion, and by contact with the body of the mother. The young 

 infant sleeps during the greater part of the time ; and even when 

 awake there are but few manifestations of intelligence or percep- 

 tion. The special senses of sight and hearing are dull and inex- 

 citable, though their organs are perfectly formed ; and even 

 consciousness seems present only to a very limited extent. Volun- 

 tary motion and sensation are nearly absent ; and the almost con- 

 stant irregular movements of the limbs, observable at this time, 

 are evidently of a reflex or automatic character. Nearly all the 

 nervous phenomena, indeed, presented by the newly-born infant, 

 are of a similar nature. The motions of its hands and feet, the act 

 of suckling, and even its cries and the contortions of its face, are 

 reflex in their origin, and do not indicate the existence of any 

 active volition, or any distinct perception of external objects. 

 There is at first but little nervous connection established with the 

 external world, and the system is as yet almost exclusively occu- 

 pied with the functions of nutrition and respiration. 



This preponderance of the simple reflex actions in the nervous 

 system of the infant, is observable even in the diseases to which it 

 is peculiarly subject for some years after birth. It is at this age 

 that convulsions from indigestion are of most frequent occurrence, 

 and even temporary strabismus and paralysis, resulting from the 

 same cause. It is well known to physicians, moreover, that the 

 effect of various drugs upon the infant is very different from that 

 which they exert upon the adult. Opium, for example, is very 

 much more active, in proportion to the dose, in the infant than in 

 the adult. Mercury, on the other hand, produces salivation with 

 greater difficulty in the former than in the latter. Blisters excite 

 more constitutional irritation in the young than in the old subject ; 

 and antimony, when given to children, is proverbially uncertain 

 and dangerous in its operation. 



The difference in the anatomy of the newly-born infant, and that 

 of the adult, may be represented, to a certain extent, by the fol- 

 lowing list, which gives the relative weight of the most important 

 internal organs at the period of birth and that of adult age ; the 

 weight of the entire body being reckoned, in each case, as 1000. 

 The relative weight of the adult organs has been calculated from 



