508 



of the paucreas above and internally, and the spleen above and 

 externally. This fossa is quite variable in form and extent. It 

 usually extends backward only to the surface of the suprarenal body, 

 but occasionally extends downward for a variable distance behind the 

 descending colon. It sometimes fails to reach the tail of the pancreas, 

 extending in that case merely between the splenic flexure and the 

 base of the spleen as a lieno-colic fossa. In twenty-four foetuses 

 (from the fourth month onwards) examined with reference to the 

 occurrence of this fossa, a well defined pancreatico-lieno-colic fossa 

 was found in fourteen, or about 60 ^/o ; a lieno-colic fossa in seven, or 

 about 30 7o 5 and no fossa at all in three cases. In the latter cases 

 the tail of the pancreas is usually adherent to the splenic flexure. 

 In foetuses younger than four months the fossa was sometimes found 

 more extensive, involving the outer part of the body of the pancreas. 

 It is not identical with the omental fold which forms the ligamentum 

 phreno-colicum. The fossa occurs less frequently in the latter foe- 

 tuses, and is probably as a rule obliterated before the adult stage is 

 reached. 



Summary, 



1) In the human embryo during the latter part of the first month 

 and the beginning of the second, the pancreas descends rapidly from 

 its primitive position opposite the upper thoracic vertebrae. From the 

 sixth week onward, however, the head of the pancreas is found as a 

 rule opposite the first and second lumbar vertebrae, sometimes as high 

 as the twelfth thoracic, or as low as the third lumbar, that is to say, 

 in the average adult position. 



2) The caudate fossa, in which the caudate process of the foetal 

 liver extends downward behind the posterior surface of the head of 

 the pancreas, is variable with respect to the time at which it becomes 

 obliterated. The upper portion may persist until birth. A small peri- 

 toneal diverticulum is often found in connection with the caudate 

 fossa, and arises by the incomplete fusion of the mesoduodenum with 

 the dorsal body wall. For a brief time (seventh to ninth week) the 

 anterior surface of the head of the pancreas is also in contact to a 

 variable extent with the liver (right lobe and left lobe). 



3) From the fourth foetal month onwards the transverse colon 

 is found adherent to the anterior surface of the head of the paucreas 

 in about 80 "/o of all cases, the transverse mesocolon persisting only 

 on the left side of the mid-line of the body. This condition probably 

 persists as a rule throughout adult life. 



