245 
in a millimeter of intestine as seen on gross section: this number was 
then squared and multiplied by the number of sq. mm as obtained 
by measuring the wax model of the entire intestine. The results ob- 
tained by this mode of computation 'agree very well with those ob- 
tained from the pig’s embryo by direct count. The smallest embryos, 
both pig and human, in which the villi are well marked, are over 
50 mm long; and their number exceeds, from their earliest appearances, 
25000 in number. From this time onward the number of villi in- 
creases rapidly as the intestine grows larger and longer. 
In order to gain some knowledge of the appearance of the villi 
in a young embryo, the intestine of an pig embryo 55 mm long was 
cut into serial sections 20 « thick, and a model in wax was made 
from a portion of the jejunum. A picture of the model is shown in 
Fig. 1. There are numerous villi present seemingly arranged in lines 
Fig. 1. Reconstruction of a piece of the intestine of an embryo pig 85 mm long, 
multiplied 50 times. A and B small villi. 
running parallel with the long axis of the intestine. The villi are not 
all of the same size, but range from small villi that are scarcely 
more than elevations of the mucosa, to large villi that extend half 
way across the lumen of the intestine. The small villi are confined 
to no particular situation on the wall of the intestine, but are evenly 
