1698 



HUMAN ANATOMY. 



intestinal tube and its mesentery. Within the mesogastrium course the three 

 branches of the coehac axis ; the superior mesenteric artery passes within the mesen- 

 tery between the Hmbs of the intestinal loop, while the inferior mesenteric artery is 

 distributed to the last part of the intestinal tube. 



The subsequent changes which the intestinal tube exhibits during its growth have 

 been carefully studied in reconstructions by Mall/ whose conclusions differ materially 

 from the prevailing views. According to this investigator, the rapidly augmenting 

 liver-mass occupies so large a portion of the still small abdominal cavity that there is 

 no space left for the expansion of the intestinal tube. In consequence of this con- 

 dition the greater part of the gut is early displaced from the abdominal cavity into 

 the coelom within the umbilical cord, the upper limb of the U-loop then lying to the 

 right and the lower to the left. The growth of the small intestine — more rapid than 

 that of the large — soon results in the production of six primary coils, the identity of 

 which is retained not only throughout development, but can be established even in 

 the adult (Mall). The first part of the gut-tube, continuous with the stomach and 

 receiving the ducts of the liver and the pancreas, increases relatively little in its 



Fig. 1432. 



Future diaphragm 



Anterior mesentery 

 (falciform ligament) 



Liver 



Anterior mesentery 

 (gastro-hepatic omentum) \_ ' 



Bodv-cav 



. \\ n 



Connection oL 

 vitelliae stalk 



Stomach 



Spleen 



Mesogastrium 



Cceliac axis 



Pancreas 



Duodenum 



Superior mesen- 

 teric artery 



Mesenterium 

 commune 



Inferior mesenteric artery 



Allantoic duct 

 Cloaca 



Beginning of large intestine 

 Diagram showing early relations of anterior and posterior mesentery. (Based on figures of Mall and Toldt.) 



length, and therefore does not become secondarily convoluted, as do the remaining 

 coils of the small intestine. This part is later represented by the duodenum. The 

 other primary coils undergo great elongation, and consequently present secondary 

 convolutions of increasing complexity, all of which for a considerable time (until the 

 embryo has attained a length of about 30 mm. ) are retained within the umbilical 

 ccelom. About this period the lower part of the body grows rapidly, resulting in 

 increased space within the peritoneal cavity, which now affords room for the tempo- 

 rarily displaced gut-coils. In consequence of these changes the intestine returns to 

 the abdominal cavity, and in embryos of 40 mm. length the coils no longer lie within 

 the umbilical cord. Mall has shown that their return to the abdominal cavity occurs 

 in a definite order, the upper part of the small intestine being first withdrawn, the 

 large intestine with its caecal dilatation last. On re-entering the abdomen the upper 

 part of the small gut passes to the left hypochondriac region, while the lower segment 

 of the small intestine with the caecum takes up a position towards the right hypo- 

 cbondriac region. Coincident with this migration the large intestine is differentiated 



' Arch, fiir Anat. u. Physiol., Supplement Bd., 1897. 



