176 



PANCKEAS 



opening of the duct of Santorini in the majority of instances becomes obliterated, 

 and the duct of Wirsung persists. When the rotation of the stomach has 

 been effected the gland loses its mesial position, and comes to lie across the 

 back of the abdomen. In man, owing to the fusion of the mesogastrium with 

 the transverse mesocolon (see Development of the Ccelom), the posterior layer 



1 ! - 



FIG. 222. TRANSVERSE SECTION OF A HUMAN EMBRYO OF 80 MM. ABOUT THE BEGINNING OF THE 



THIRD MONTH. (T. H. Bryce.) 



Below the spinal cord is seen the, body of a vertebra ; on each side of this the kidney ; on the left 

 (right of figure) below the kidney the adrenal ; on the right only a small portion of the right adrenal is 

 seen below and external to a large vein. Between the two adrenals and below the aorta (distinguished 

 from the veins by its thick wall) some irregular groups of cells represent the abdominal sympathetic ; 

 on the right side (left of figure), just above the large vein, the two rounded clear bodies are chromaffin 

 bodies. The liver occupies the whole abdominal cavity ; its right and left lobes are separated by the 

 ventral mesentery (falciform ligament) in which the umbilical vein passes. The stomach is twice cut in 

 the section ; between it and the adrenal is seen the mesogastrium, with the spleen. The duodenum, 

 with its much-folded mucosa, is seen on the right ; between it and the stomach the pancreatic tubules 

 and pancreatic ducts (ducts of Santorini and Wrisberg) ; between stomach, pancreas, and thin portion 

 of the mesogaster the lesser bag of the peritoneum. 



of the mesenteric fold which enclosed the pancreas becomes absorbed, and the gland 

 comes to he entirely behind the peritoneum. 



Owing to the manner in which the alveoli are budded off round the ends of the duct-rudiment, 

 the terminal portion of duct-epithelium is as it were included in the centre of the alveolus to 



