236 FRANKLIN PARADISE JOHNSON 



an empty piece of intestine, taken immediately adjacent to the 

 distended piece, was treated with the same fixing fluids. Micro- 

 scopical examination showed most interesting results, as can 

 be seen by comparing figin-es 1 and 2. The villi have been greatly 

 shortened and the glands stretched out and obliterated. These 

 results led to a number of experiments which are described 

 below. 



A survey of the literature shows that the idea that villi are 

 capable of changing their form under different conditions is 

 an old one. These changes, however, have been usually con- 

 sidered to be produced by the intrinsic muscle fibers of the 

 villi. That villi undergo shortening was noted by Lacauchie 

 ('43), who recognized the muscular nature of the walls of the 

 lacteals, by Gruby and Delafond ('43), and by Briicke ('50). 

 Kolliker ('51) showed that the muscle fibers of the villi run 

 down between the intestinal glands and that they are related 

 to the fibers in the muscularis mucosae. By a contraction of 

 these fibers, it was then and is now commonly believed that a 

 shortening and broadening of the villi may be produced. 



"We owe to Heitzmann ('68), however, the discovery that 

 the shapes of villi vary with the distention of the intestine, a 

 fact which apparently has been lost sight of in the current text- 

 books and publications. Heitzmann found that a piece of intes- 

 tine of a freshly killed guinea-pig possessed alternating con- 

 tracted and distended portions, and that if the piece be thrown 

 into a chromic acid mixture the contracted portions remain 

 permanently contracted, and the distended portions distended. 

 His examination of the villi of the contracted portion showed 

 them to be long and cylindrical; of the distended portion, flat 

 and conical. Moreover, he observed that artificial distention, 

 produced by filling a tied-off piece of intestnie with chromic 

 acid mixture beyond the limits of ordinary normal expansion, 

 or extreme distention caused by the formation of gas in the 

 intestine, almost entirely obliterated the villi. This he found 

 to be true not only for the villi of the guinea-pig, but to a less 

 extent for those of the rabbit and cat. He concluded, there- 

 fore, that there is no fixed form for the villi, but that their shapes 



