DEVELOPMENT OF THE BODY AFTER BIRTH. 689 



the estimates of Cruveilheir, Solly, "Wilson, &c. ; that of the organs 

 in the foetus at term from our own observations. 



ADULT. 

 1000.00 

 23.00 

 29.00 

 4.17 

 4.00 

 0.13 

 0.51 

 0.00 



It will be observed that most of the internal organs diminish in 

 relative size after birth, owing principally to the increased develop- 

 ment of the osseous and muscular systems, both of which are in a 

 very imperfect condition throughout intra-uterine life, but which 

 come into activity during childhood and youth. 



Within the first day after birth the remains of the umbilical 

 cord begin to wither, and become completely desiccated by about 

 the third day. A superficial ulceration then takes place about the 

 point of its attachment, and it is separated and thrown off within 

 the first week. After the separation of the cord, the umbilicus 

 becomes completely cicatrized by the tenth or twelfth day after 

 birth. (Guy.) 



An exfoliation and renovation of the cuticle also take place 

 over the whole body soon after birth. According to Kolliker, the 

 eyelashes, and probably all the hairs of the body and head are 

 thrown off and replaced by new ones within the first year. 



The teeth in the newly-born infant are but partially developed, 

 and are still inclosed in their follicles, and concealed beneath the 

 gums. They are twenty in number, viz., two incisors, one canine, 

 and two molars, on each side of each jaw. At birth there is a thin 

 layer of dentine and enamel covering their upper surfaces, but 

 the body of the tooth and its fangs are formed subsequently by 

 progressive elongation and ossification of the tooth-pulp. The 

 fully-formed teeth emerge from the gums in the following order. 

 The central incisors in the seventh month after birth; the lateral 

 incisors in the eighth month ; the anterior molars at the end of the 

 first year ; the canines at a year and a half; and the second molars 

 at two years (Kolliker). The eruption of the teeth in the lower 

 jaw generally precedes by a short time that of the corresponding 

 teeth in the upper. 



During the seventh year a change .begins to take place by which 

 44 



