William A. Hilton 483 



A few facts which seem to point to an intimate relation between the 

 disappearance of villi and the growth of the intestine may be given. 



In white rat, very few new villi are formed after birth by buds of 

 epithelium in the large intestine, the large intestine and caecum at first 

 grow very rapidly in length and diameter, but hardly at all in thick- 

 ness of the intestinal wall, and during this rapid growth villi grow 

 smaller and smaller until finally they disappear (Fig. 82). 



The following measurements are given to show the rapidity of 

 growth. 



White rat of 5 days. (Length 6.6 cm.) Large intestine 3.3 cm.; 

 caecum, .5 cm. Villi in csecum and upper large intestine. 



White rat of 7 days. Large intestine, 4 cm. ; caecum, .7 cm. Villi in 

 caecum going but numerous in upper large intestine. 



White rat of 8 days. Large intestine, 4.2 cm.; caecum, .8 cm. A^illi 

 in caecum nearly gone. Villi in the upper large intestine beginning to 

 go. 



White rat of 9 days. (Length 7.8 cm.) Large intestine, 4.9 cm. ; cae- 

 cum, 1 cm. No villi in the caecum but few in the upper large intestine. 



White rat of 10 days. (Length, 7.3 cm.) Large intestine, 4.7 cm.; 

 caecum, .9 cm. A very few villi in some places of caecum and a few in 

 the upper large intestine. 



White rat of 11 days. (Length, 8.5 cm.) Large intestine, 5 cm.; cae- 

 cum, 1 cm. No villi except a very few small ones in the upper large 

 intestine near the folds. 



As to the de?rease in height of villi, the following is given for the 

 caecum, a similar decrease takes place in the large intestine. 



5 days, longest villus .3 mm. high. 



6 days, longest villus .2 mm. high. 



7 days, longest villus .08 mm. high. 

 10 days, longest villus .035 mm. high. 



If the glands were formed by part of the villi we might expect the 

 crypts to be much longer after the villi had been obliterated, but as a 

 matter of fact the crypts are not in the least longer just after the villi 

 have disappeared. 



The caecum is a rapidly growing part of the intestine and villi disap- 

 pear here after they have ceased to exist in the lower large intestine; 

 that part of the large intestine which retains its villi until the last is 

 the large intestine just below the c^cum, here as already shown the villi 

 persist for a long time after they have disappeared elsewhere. In this 

 region in the adult there are numerous nearly longitudinal folds which 



