96 PHYSIOLOGY AND NATIONAL NEEDS 



muscles of tlie arms and legs may be affected. The 

 muscles of the larynx are also sometimes in spasm 

 and cause a peculiar crowing sound in breathing, 

 especially when the child cries. Frequently the 

 condition goes on to the development of general 

 convulsions, in one of which the child may die. 

 The condition may be latent for long periods, but 

 it may then be detected by the fact that the nerves 

 and muscles are peculiarly excitable — so that a tap 

 on the side of the face will cause a characteristic 

 spasm at the angle of the mouth, while an electric 

 current produces a peculiarly exaggerated effect 

 when appHed over the nerves or the muscles. 



A somewhat similar condition is sometimes 

 found in adults of certain districts, more frequently 

 attacking those engaged in sedentary employment, 

 such as shoemakers. 



Many different theories have been from time to 

 time advanced as to the cause of the condition, 

 since Clarke first described it in 1815 ; but the first 

 important light was thrown by Austrian and Swiss 

 surgeons when the operation of removing goitres — 

 tumours of the thyroid gland — came into vogue. 



They found that a certain proportion of the 

 patients after operation suffered from a condition 

 of tetany. This they thought to be due to removal 

 of the thyroid gland. But closely associated with 

 the thyroid are little structures which from their 

 position have been called the parathyroids, and 



