130 LAWSON G. LOWREY 



per cent of the total weight in the 26 cm. fetus (nearly full term). 

 In the adult it forms 0.32 per cent, about one-third that of the 

 late fetus. 



In the human the heart also has its maximum early, being 

 estimated at more than 5 per cent in a four-weeks embryo; 

 3 . 64 per cent in the fifth week (11 mm.) and . 85 per cent in the 

 third month. At birth, it forms 0.7 per cent or 0.77 per cent 

 (still-born or live-born). Vierordt estimates the adult human 

 heart to form . 56 per cent of the total weight. 



The heart is therefore similar in relative size in pig and human 

 during fetal life. It appears, however, to be relatively smaller 

 at birth, and larger in the adult, in the human. 



Stomach and intestines. {Table 1: fig. 2). The stomach and 

 intestines (including mesentery) differ from all other organs 

 observed, in that they increase greatly in relative size in the adult 

 as compared with the fetus. This is the case whether they are 

 considered with or without contents. 



At 18 mm. they form 0.26 per cent of the total body weight, 

 after which they increase, at first very rapidly, then more slowly 

 (and with considerable individual variation) to a maximum 

 (for prenatal life) of 6 per cent in the late fetus. In the adult 

 they form 6.81 per cent of the total weight. These figures are 

 for stomach and intestines plus contents, which, especially in the 

 later stages, present a great deal of variation. 



A better index of the growth is shown by the figures for the 

 stomach and intestines without contents. In the stages up to 

 and including the 42 mm. stage, there would seem to be no appre- 

 ciable contents, and here the stomach and intestines amount to 

 1 . 62 per cent of the body weight. These organs gradually 

 increase throughout fetal life, forming at 26 cm. about 3 . 59 per 

 cent of the total body weight, being about 40 per cent less than 

 the same with contents (5.99 per cent). In the adult they form 

 (empty) about 4.79 per cent of the net body weight, about 30 

 per cent less than the tract with contents. 



' The range of variation is large, due to the extreme variations in 

 contents, but the empty ti-act is, in later prenatal life, about 

 35 to 40 per cent less in weight than the tract with contents. 



