362 



DYNAMICS OF HISTOGENESIS. 



TABLE I. 



Measurements of Differential Growth of Descending Colon. 



* The mesenchymal wall begins to diminish in thickness after it reaches a 

 width of 0.128 mm. in the 14 mm. stage of the pig embryo. This diminution is 

 due to the tension caused by the more rapid epithelial tubular growth in diameter. 

 Measurements made with B. and L. filar micrometer, calibrated. 



t The ratio of the square of the mean diameter of the epithelial tube to that of 

 the surrounding mesenchyme is referred -to as the epithelial tubular index. It has 

 been calculated from the following formula. 



( 2 ) 



X 100 



(X + F)2 -{x+ yy 



( 



) ( 2 ) J 



X and y are the long and short diameters of the epithelial tube respectively. ^^J5^ 

 and Y are the long and short diameters of the surrounding mesenchymal tube. 

 Z is the ratio of the epithelial tube to the mesenchymal tube. 



