CH. XXXII. ] EXTIRPATION OF THE PANCREAS 501 



upsets not only its specific function, but causes disturbances through 

 the body generally. The interdependence of the circulatory and 

 respiratory systems is a well-known instance. Kemoval of the thyroid 

 gland upsets the whole body, producing widespread changes known as 

 rnyxoedema. Eemoval of the testis produces not only a less of the 

 spermatic secretion, but changes the whole growth and appearance of 

 the animal. Removal of the greater part of the kidneys produces 

 rapid wasting and the breaking down of the tissues to form an 

 increased quantity of urea. The precise way in which these glands 

 are related to the general body processes is, however, a subject of 

 which we know as yet very little. The theory at present most in 

 favour is that certain glands produce an internal secretion, which 

 leaves them vid the lymph, and is then distributed to minister to 

 parts elsewhere. The question of the internal secretions of the 

 thyroid and suprarenal capsules is discussed in Chap. XXIII. In 

 the case of the pancreas, Schafer has propounded the theory that its 

 internal secretion, stoppage of which in some way leads to diabetes, 

 is produced in the islets of epithelium-like cells scattered through 

 the connective tissue of the organ (see fig. 398, p. 491). 



Doubt is cast upon the above hypothesis concerning the function of these ** islets 

 of Langerhans " by some recent work of Dale's. He showed that the number of 

 islets increases with activity ; he regards them as phases in the life history of the 

 secreting cells, and considers that they represent a stage of extreme exhaustion 

 of these cells. In the foetal pancreas, all the cells have the appearance of islet 

 cells, and so it is probable that in the adult the islets recover their properties, and 

 an alveolar arrangement, and with this their secretory activity. 



Adaptation of the Pancreas. On p. 494 some instances are given of the 

 power of the pancreas to adapt its secretion to the needs of digestion. Bainbridge 

 has shown that in certain cases this is done by a chemical messenger ; the pan- 

 creatic juice of a dog normally contains no ferment (lactase) capable of hydrolysing 

 milk-sugar into dextrose and galactose, but a dog fed for some time on milk has 

 lactase in its pancreatic juice. This is due to the milk-sugar acting on the intestinal 

 mucous membrane in such a way as to produce some chemical material, which is 

 taken by the blood to the pancreas, where it excites the secretion of this unusual 

 enzyme ; for if one injects an extract of the intestinal membrane of a milk-fed dog 

 into a normal dog, the latter animal immediately secretes lactase in its pancreatic 

 juice. 



