PANCREAS OF THE PIG 



233 



more condensed and the units are crowded together. Anas- 

 tomoses between the capillary tufts become frequent, the connect- 

 ive tissue septa are thinned out, and the former clear division 

 into units is blurred — in some species more than others — so that 

 in section one sees masses of varying area according to the animal. 



Fig. 17 Diagram to illustrate the growth of one unit into four. A is a recon- 

 struction from actual sections of one unit from a 150 mm. foetus; B and C repre- 

 sent the probable growth of .1 . In A the duct, Dt enters the unit at a point opposite 

 the artery, Art. In (' the two vessels enter one of the units almost together, e. 



Fig. 18 Outline drawing of a branch duct and several units from the same 

 190 mm. pig foetus, illustrating the chain-like method of expansion commonest 

 in the tail of the pancreas (see also figure 1). X 35. 



Fig. 19 Outline drawing of a branch duct and several units from the same 

 190 mm. pig foetus, illustrating the grape-like method of growth commonest in 

 the head and body of the pancreas. X 35. 



Perhaps a species may be found in which the imit persists clearly 

 through life, as the unit of the liver in the seal. 



Although the blood-circulatory system is the measure which 

 lays ofT the duct-tree of the pancreas into regular units, at the 

 same time, it does not seem unreasonable to suppose that some 



