PANCREAS OF THE PIG 



215 



for the present that the smoothly rounded average-sized nodules 

 represent typical divisions of the foetal gland, while the larger 

 and smaller masses are stages in the multiplication of one mass 

 into two or more. From now on, for the sake of clearness, these 

 bodies will be referred to as 'structural units,' since one of the 

 results of this study is to prove them such. 



In injected specimens a branch of the duct can be traced into 

 each unit (fig. 16) where it branches by dichotomous division a 

 number of times to reach the acini. The first or intralobular 



Fig. 3 Part of pancreas of a 105 mm. pig foetus. Blood-vessels injected with 

 silver nitrate, showing arterioles and capillary tufts of two units; one is supplied 

 by an arteriole which branches before entering the capillaries, the other has two 

 tiny arterioles. Preparation by Dr. Florence R. Sabin. A, arteriole supplying 

 one unit. X 55. 



branches are several in number, tending toward all parts of the 

 unit, and give off slender straight ducts (fig. 16) corresponding 

 to the 'Schaltstiicke' of the adult; each of which in turn gives 

 origin to a few slender short pre-acinar ducts, whose ultimate 

 twigs are the acini. In figure 13, B, the artist has shown the 

 duct-system in its full complexity. An arteriole penetrates into 

 each unit (fig. 1) where it may branch once into the tiniest of 

 arterial vessels, and immediately breaks up into a ball-like cap- 

 illary net of great richness (fig. 3, A). This capillary net may 

 anastomose with a few or with many capillaries from adjoining 

 similar nets, according to whether it is situated in the denser 

 body of the gland, or is lying relatively free in the tail. A cleared 

 arterial injection presents a beautiful appearance under the 

 binocular microscope, being a thick cluster of these capillary 



