LIFE: ITS NATUKE, ORIGIN AND MAINTENANCE 31 



most observers) to be fatal often within two or three days. Its hyper- 

 trophy, when occurring during the general growth of the body, is attended 



by an undue development of the skeleton, so that 

 Pituitary. J 



the stature tends to assume gigantic proportions. 



When the hypertrophy occurs after growth is completed, the extremities 

 viz., the hands and feet and the bones of the face are mainly affected ; 

 hence the condition has been termed ' acromegaly ' (enlargement of 

 extremities). The association of this condition with affections of the 

 pituitary was pointed out in 1885 by a distinguished French physician, 

 Dr. Pierre Marie. Both ' giants ' and ' acromegalists ' are almost in- 

 variably found to have, an enlarged pituitary. The enlargement is 

 generally confined to one part the anterior lobe and we conclude 

 that this produces hormones which stimulate the growth of the body 

 generally and of the skeleton in particular. The remainder of the 

 pituitary is different in structure from the anterior lobe and has a 

 different function. From it hormones can be extracted which, like those 

 of the suprarenal capsule, although not exactly in the same manner, 

 influence the contraction of the heart and arteries. Its extracts are also 

 instrumental in promoting the secretion of certain glands. When 

 injected into the blood they cause a free secretion of water from the 

 kidneys and of milk from the mammary glands, neither of which organs 

 are directly influenced (as most other glands are) through the nervous 

 system. Doubtless under natural conditions these organs are stimulated 

 to activity by hormones which are produced in the pituitary and which 

 pass from this into the blood. 



The internally secreting glands which have been mentioned (thyroid, 

 parathyroid, suprarenal, pituitary) have, so far as is known, no other 

 function than that of producing chemical substances of this character 

 for the influencing of other organs, to which they are conveyed by the 

 blood. It is interesting to observe that these glands are all of very small 

 size, none being larger than a walnut, and some the parathyroids 

 almost microscopic. In spite of this, they are essential to the proper 

 maintenance of the life of the body, and the total removal of any of them 

 by disease or operation is in most cases speedily fatal. 



There are, however, organs in the body yielding internal secretions 

 to the blood in the shape of hormones, but exercising at the same time 

 other functions. A striking instance is furnished by 

 the pancreas, the secretion of which is the most 

 important of the digestive juices. This the pancreatic juice forms the 

 external secretion of the gland, and is poured into the intestine, where its 

 action upon the food as it passes out from the stomach has long been 

 recognised. It was, however, discovered in 1889 by von Mering and Min- 

 kowski that the pancreas also furnishes an internal secretion, containing 

 a hormone which is passed from the pancreas into the blood, by which 

 it is carried first to the liver and afterwards to the body generally. This 



