Prenatal Growth of the Pluman Body. 151 



Weight (g).((A««J^'>y 



2. The head attains its maximum relative size, about 45 per cent 

 of the total body weight, during the 2d month, thereafter decreasing 

 to about 26 per cent at birth. A relatively large embryonic head is 

 characteristic for vertebrates in general. 



3. The trunk is relatively larger in the 1st month (about 65 per 

 cent of the whole body) decreasing to between 40 per cent and 45 

 per cent in the later fetal months. 



4. The extremities increase gradually in relative size from the 

 beginning, the upper extremities forming at birth about 10 per cent of 

 the entire body, and the lower about 20 per cent. 



5. The brain curve of relative growth is nearly parallel with 

 that for the head, reaching a maximum of about 20 per cent in the 

 2d month and decreasing thereafter to an average of 13 per cent 

 or, 14 per cent of the whole body at birth. 



6. The spinal cord is relatively largest (about 5 per cent of the 

 entire body) in the 1st month, decreasing at first rapidly, then more 

 slowly to about .15 per cent at birth. 



I. The curve of relative growth of the heart is close to that of 

 the spinal cord during the 1st, 2d and 3d months, remaining near 

 an average of .7 per cent thereafter. 



8. The liver increases to a maximum of 7.5 per cent (average) 

 of the entire body during the 2d and 3d months, remaining fairly 

 constant between 5 per cent and 6 per cent during the remainder of 

 the fetal period. 



9. The lungs increase gradually in relative size to a maximum 

 average of about 3.3 per cent in the 4th month, decreasing thereafter 

 to an average of about 2 per cent of the entire body at birth. 



10. The spleen, thymus and thyroid gland increase from the be- 

 ginning more or less regularly in relative size, averaging about .4 

 per cent, .3 per cent, and .12 per cent, respectively, of the total body 

 ^\'eight at birth. 



II. The kidneys increase at first rapidly, then more slowly to a 

 maximum of about 1.0 per cent in the 7th month. Later they de- 



