CH. xxxn.] NERVES OF THE PANCREAS. 493 



Pawlow discovered that the vagus contains the secretory nerves 

 of the pancreas ; he took care to avoid the sources of error just 

 referred to. In the first place he stimulated the vagi below the 

 origin of their cardiac branches ; in the Tecond, the spinal cord 

 was divided high up to prevent reflexes occurring from sensory 

 nerves, and lastly, the operation of stimulating the nerve was 

 done without an anaesthetic. 



In another series of experiments, he cut through one vagus in 

 the neck, and stimulated the peripheral end two or three days 

 later, when the cardio- inhibitory fibres had degenerated : in this 

 way he got rid of the heart stoppage which would have interfered 

 with the normal condition of the animal. 



In all cases, the stimulation of the vagus produced an abundant 

 flow of pancreatic juice, after a latent period of from fifteen 

 seconds to two minutes. The stimulation applied to the nerve 

 consisted of a slow series of shocks (either induction currents or 

 mechanical blows) about once a second. By this means stimula- 

 tion of vaso-constrictor nerves to the pancreas contained in the 

 vagus is avoided. If the blood supply is diminished by stimula- 

 tion of vaso-constrictor nerves, the secretion is stopped. 



Extirpation of the Pancreas. 



Complete removal of the pancreas in animals and diseases of 

 the pancreas in man produce a condition of diabetes, in addition 

 to the loss of pancreatic action in the intestines. Grafting the 

 pancreas from another animal into the abdomen of the animal 

 from which the pancreas has been removed relieves the diabetic 

 condition. 



How the pancreas acts other than in producing the pancreatic 

 juice is not known. It must, however, have other functions 

 related to the general metabolic phenomena of the body, which 

 are disturbed by removal or disease of the gland. This is an 

 illustration of a universal truth viz., that each part of the 

 body does not merely do its own special work, but is concerned 

 in the great cycle of changes which is called general metabolism. 

 Interference with any organ upsets not only its specific function, 

 but causes disturbances through the body generally. The inter- 

 dependence of the circulatory and respiratory systems is a well- 

 known instance. Removal of the thyroid gland upsets the whole 

 body, producing widespread changes known as myxoedema. 

 Removal of the testis produces not only a loss of the spermatic 

 secretion, but changes the whole growth and appearance of the 

 animal. Removal of the greater part of the kidneys produces 



