DEVELOPMENT OF THE INTESTINES 431 



latter process is under way in the 40 mm. embryo shown in figures 

 5, 6 and 7. 



Normally the jejunal or abdominal coils of the small intestines 

 develop simultaneously with the left colic loop, described above 

 (figs. 3, 4, 5, 6, 7). That this coincident development is not 

 constant is indicated by the numerous cases which have been 

 described, in which, with an approximately normal disposition of 

 the upper part of the descending colon, indicating a fairly normal 

 ear]y development of the colic loop, the proximal part of the small 

 intestines has occupied a markedly abnormal position. In these 

 cases, an excellent example of which is given by StrehP and 

 another by Huntington,^ the primitive duodeno-jejunal loop 

 appears to be diverted from its usual course of development be- 

 neath the umbilical stalk and to have been forced to develop, in 

 so far as development has taken place, on the proximal side of the 

 stalk. In the illustration given by Huntington (fig. 10) the duo- 

 deno-jejunal loop appears in about the state of development 

 normally found in embryos 24 to 28 mm. long (figs. 1 and 2). In 

 the illustration given by Broman (fig. 11) the duodeno-jejunal loop 

 appears even less advanced in normal development, ^\^len the 

 duodeno-jejunal loop fails to develop to the left beneath the 

 umbilical stalk there appears in general to be a subsequent lack 

 of development of the proximal part of the small intestines. In 

 such cases the intestinal coils are probably in the main coils which 

 have developed in the umbilical cord and then have returned to 

 the abdominal cavity. It is probable that in these cases factors 

 which normally leave room for the development of coils belo\A- 

 and to the left of the umbilical stalk become inoperative. Pos- 

 sibly the pressure of the liver is greater than normal. Possibly 

 the lower part of the trunk fails to expand as rapidly as normal. 



In most of these cases the umbilical part of the colon fails to 

 reach its usual position when the umbilical coils return to the 

 abdominal cavity. Normally, as is well known, it swings across 

 the ventral side of the loops of the small intestine in the left side 



' Arch. f. klin. Chirurgie, Bd. 87, 190S, cited by Broman; Normale und abnorme 

 Kntwichlung des Alenschen, fig. 326, p. 380. 



' Anatomy of the peritoneum and abdomen, fig. 121. 



