IV 



DIGESTION IN THE INTESTINE 



215 



of the bundles that form the muscular hoop, and their independence 

 of the muscular coats of the intestine, it is very conspicuous under 

 the microscope, even with a low power, in sections parallel with 

 the long axis of the intestine (Fig. 73, A). In man, on the 

 contrary, owing to the delicacy of the muscle fibres, and the twist 

 in the lumen of the bile-duct, during its very brief passage through 

 the intestinal walls, the 

 sphincter-like arrangement 

 is less striking and char- 

 acteristic (Fig. 73, B.). 



Oddifurther succeeded in 

 showing that the sphincter 

 of the bile-duct, like all 

 other sphincters, has a tone 

 of its own, which is able to 

 resist a column of 50 mm. 

 Hg ( = 675 mm. H 2 0). This 

 explains why the sphincter 

 resists the pressure of the 

 bile, even when the gall- 

 bladder is full and dis- 

 tended, showing that its 

 tonic resistance exceeds the 

 normal secretory pressure of 

 bile by quite 475 mm. H 2 0. 



To complete his experi- 

 ments, Oddi also proved that 

 the tone of the sphincter of 

 the common bile-duct is 

 allied to the function of cer- 

 tain ganglia in its vicinity, 

 which have specific cyto- 

 logical characteristics by 

 which they are differentiated 

 from the plexuses of Auer- 

 bach and Meissner, of which 

 we shall speak later (Fig. 74). 

 According to Oddi, the presence of these ganglia explains why, 

 after separating the tract into which the bile-duct opens from 

 the remainder of the intestine, that orifice can remain closed 

 for a long while owing to the tonic -spastic contraction of the 

 sphincter. 



In a later series of researches, Oddi succeeded in proving the 

 existence of a spinal centre, by which the tone of the sphincter of 

 the common bile-duct is regulated. In dogs this centre is 

 level, or at least in relation, with the first pair of lumbar nerves. 

 The afferent paths, according to Oddi, are represented by the 



P2 



FIG. 74. Oblique section through dog's bile-duct, at 

 the angle of convergence between the thick muscular 

 coat of the intestine and the thin muscularis 

 mucosae, 35 diameters magnification. (Oddi.) a, 

 group of ganglion cells which regulate the tone of 

 the sphincter of the bile-duct ; b, muscular coat 

 of intestine ; 6, muscularis mucosae ; c, Oddi's 

 sphincter. 



