Oct. is, 1924 Postnatal Growth of the Single-Comb White Leghorn 
393 
show the rapid growth during the 
smaller body weights to so marked a 
degree as does the curve of brain 
growth. There is in this case an 
Welcker and Brandt {28) give 0.13 
per cent for the relative weight of the 
spinal cord in two adult male chickens. 
Both the brain and the cord are- 
Fig. 30.—Absolute and relative or percentage weights of the spinal cord, plotted on gross body weight 
apparent sex difference (of doubtful sig¬ 
nificance) at the upper end of the curve. 
The relative weights of the spinal 
cord show no initial increase (as found 
relatively heavier in the rat than in 
the chicken. 
Eyeballs. —Figure 31 shows that 
the growth in absolute and in relative 
Fig. 31.—Absolute and relative weights of the two eyeballs, plotted on gross body weight. 
in the rat). At time of hatching the 
cord forms 0.5 per cent of the body 
weight. This decreases rapidly at first, 
then more slowly until it reaches about 
0.12 per cent. 
weight of the eyeballs is essentially 
similar to that of the brain and spinal 
cord. The individual cases, however, 
indicate a greater variability than is 
found in weights of brain and spinal 
