286 CARPENTER, ON HUMAN PHYSIOLOGY. 
tissue (Fig. 20 ¢), and constitute the so-called Reta amplum. Besides 
the central lacteal, the villus is composed of a matrix of areolar 
tissue,* without any intermixture of elastic fibres, containing in its 
interstices numerous branched and communicating cells with nuclei, 
and frequently also fat-granules in their interior. No nervous 
elements have been traced into the villi; but a layer of muscular 
fibre-cells has been shown by Kédlliker and others to surround the 
Fig. 19. 
A. Villi of Man, showing the blood-vessels and the lacteals. 
B. Villus of a Sheep. 
lacteal tubes, the contraction of which has been frequently observed 
whilst absorption is going on, and has an important influence on the 
propulsion of the fluids contained within those vessels. 
107. When the villi are examined at such a period after a meal 
containing oleaginous matters as has sufficed for its partial digestion, 
their lacteals are seen to be turgid with chyle, the extremity of each 
being embedded in a collection of globules presenting an opalescent 
appearance, and giving to the end of the villus a somewhat mulberry- 
like form, It was supposed by Prof. Goodsir,+ by whom this appear- 
ance was first observed, that these globules were cells developed 
* KGlliker, ‘Manual of Hum. Histology,’ p. 325. 
t+ ‘Edin. New Phil. Journ.” July, 1842, and ‘ Anatom. and Pathol. Observ., 
pp. 5—10. 
