216 PHYSIOLOGY CHAP. 



sensory nerves in general, and particularly by the centripetal 

 fibres of the vagus and sympathetic : the efferent by the ante.rior 

 roots of the first lumbar pair. The mechanism by which the flow 

 of bile into the intestine is brought about consists in a reflex 

 diminution of tone in the sphincter of the common bile-duct, 

 caused by the distension of the intestine and entrance of the acid 

 chyme from the stomach. It is, therefore, an inhibitory reflex, 

 discharged from a higher centre (of which the localisation is 

 entirely unknown), by which the tonic action of the lumbar centre 

 is suspended. 



More minute researches into the contractility of the excretory 

 bile-ducts, by the graphic method, were carried out in Morat's 

 laboratory, and published by Doyon in 1893. According to Doyon 

 the contractility of these ducts is perfectly similar to that of all 

 other organs with plain muscle cells. They exhibit automatic, 

 rhythmic oscillations of tonus, similar to those above described for 

 the stomach. This rhythm can be seen in mammals, but is 

 particularly visible in birds (pigeons). After inoculation of pilo- 

 carpine, Oddi's sphincter enters into spastic contraction, and for a 

 long time resists the efflux of bile into the duodenum. 



The great splanchnics, according to Doyon, contain the motor 

 nerves to the bile-ducts, since on stimulating them the whole of 

 the excretory biliary system contracts. It is possible that the 

 splanchnics receive fibres from the anterior roots of the first lumbar 

 nerves, and from Oddi's spinal centre. Dilatation of the common 

 bile-duct is usually obtained by reflex only, by excitation either of 

 the central end of the splanchnic (which causes dilatation of the 

 gall-bladder), or by the central end of the vagus (which produces 

 dilatation of Oddi's sphincter with simultaneous contraction of the 

 gall-bladder). Asphyxia causes constriction of all the bile passages, 

 as of the blood-vessels ; curarisation produces the opposite effect. 

 Injection of pilocarpine acts like asphyxia, atropine poisoning like 

 curare. 



Bruno (1899), in Winogradsky's laboratory, with the object of 

 better determining the relations between biliary excretion and 

 digestion, excised in a dog the part of the duodenal wall which 

 contains the papilla of Vater, with the orifice of the common bile- 

 duct, and sutured it to the edges of the abdominal wound, after 

 stitching up the aperture into the intestine. On recovering from 

 the operation, this dog was for about a month the subject of many 

 interesting observations, from which the following conclusions may 

 be taken : 



(a) The flow of bile occurs only when the stomach contains 

 food, (b) The flow of bile commences after a latent period of 15 

 or more minutes, and continues till the stomach is completely 

 emptied of chyme, after which biliary excretion ceases, (c) Not 

 all food-stuffs are active, i.e. able reflexly to determine dilatation 



