436 C. R. BARDEEN 



The relative rate of growth of body axis is somewhat less than that 

 of the intestines in embryos between 17 and 24 mm. or less. There 

 then begins a relatively very rapid development of the coils of 

 the small intestines within the umbilical cord. In one fetus of 

 24 mm. these are nearly twice as long as in another (compare x 

 and VI in the table) . The relatively more rapid growth of the small 

 intestines continues in fetuses between 24 and 28 mm. in length, 

 while the rate of growth of the large intestines still continues to 

 be about equal to that of the axis of the body. During the next 

 stage, however, in fetuses between 28 and 40 mm. in length the 

 small intestines grow nearly twice and the large intestine over 

 twice as fast as the axis of the body. As may be seen from foot- 

 note 6 of the table, during this period the duodenum and the 

 jejunum (abdominal part of the small intestines, primitive loops 

 1 to 3 of Mall) grow much more rapidly than the ileum (umbilical 

 coils, loops 4 to 6 of Mall) . The relatively great growth in length 

 of the large intestines is due to the development of the left colic 

 loop. After the return of the umbilical coils into the abdominal 

 cavity, in fetuses between 40 and 80 mm. in length, both the large 

 and small intestines grow somewhat more rapidly in length than 

 the axis of the body, but the difference is far less marked than in 

 the preceding period. The ilemn (loops 4, 5 and 6 of Mall) 

 grows relatively much faster than the jejunum (loops 2 and 3 of 

 Mall) according to the data furnished by Mall. From this time 

 on, although there are undoubtedly great individual differences 

 in the growth in length of the intestines, on an average there does 

 not appear to be much difference in the growth in length of the 

 intestines as compared with that of the axis of the body, with the 

 exception of a great increase in the length of the large intestine 

 toward the latter part of fetal life. 



From table 1 it is clear that the period of relatively greatest 

 intestinal development is that immediately preceding and accom- 

 panying the return of the umbilical loop into the abdominal cavity, 

 the period when the fetus is growing from 20 to 50 mm. in length. 

 This is the critical period in the development of the intestines. 

 Variations which occur later are of minor importance. 



