296 



PHYSIOLOGY 



CHAP. 



in the same villus, showing epithelia in the first, second, or third 

 phase of the process of absorption and internal secretion of the 

 absorbed products. It is usually the epithelia of the apex of the 

 villus which show these changes most conspicuously; along the 

 lateral walls of the villus they are less obvious, and are minimal 

 towards its base. 



According to Mingazzini, the stroma of the villi also presents 



FIG. 95. Villus of small intestine of fowl during absorption. (P. Mingazzini.) Lettering as in 

 previous figure. In the apex of right side of villus particularly the columnar cells have 

 become elongated and exhibit a zone external to the nucleus (zs) that stains deeply, and an 

 internal hyaline zone (zj) which contains the absorbed substance. At the apex of the villus 

 the inner epithelial zone is transformed into a granular substance (si). 



different aspects in different phases. In some cases it seems to 

 consist of a compact tissue; in others, on the contrary, of loose 

 tissue. In the former it is regular in form, and of small dimensions; 

 in the latter the form is not very regular, and the dimensions are 

 larger (Fig. 96). It is possible in the last case that the villi may 

 be swollen owing to the chyle poured out by internal secretion 

 into the lymph spaces of the adenoid tissue, before it reaches the 

 central lacteal. The leucocytes packed between the epithelial 

 cells are perhaps destined to function after the latter have dis- 

 charged their internal secretion. 



These observations of Mingazzini gave rise to much discussion 



