THE THYROID AND PARATHYROID GLANDS 759 



peculiar shaking of the foot, like that made by a normal animal to shake 

 water off its pads, is a characteristic symptom. The slightest stimulation 

 of the peripheral nerves is sufficient to induce one of these attacks, which 

 recur with ever increasing frequency, becoming at the same time more 

 pronounced and accompanied by other disturbances, such as diarrhea, 

 profuse salivation, rapid pulse, and dyspnea (in the dog but not in the 

 cat). In cases that are not quickly fatal, the hair tends to be shed, and 

 the teeth to be improperly calcified (in young animals). Where a certain 

 amount of parathyroid tissue has been left for example, one of the four 

 lobes the symptoms may not appear except under conditions of special 

 strain to the animal economy, such as pregnancy or improper diet. 

 Thus, in a bitch from which three of the four glands had been removed, 

 no symptoms of tetany occurred until she became pregnant. Under the 

 same conditions it has been found that a diet of flesh is much more apt 

 to bring about the condition than one of vegetables or milk. 



Tetany, as the above condition is called, may also become developed 

 in man either as the result of surgical removal of the parathyroids or 

 because of their improper development. The symptoms in man are very 

 similar to those observed in laboratory animals, the only difference being 

 that the muscular contractions are more likely to be tonic in character. 

 Certain symptoms that may develop during pregnancy or in the course 

 of infectious diseases or in newborn infants have also been found to be 

 associated with degeneration of or hemorrhage into the parathyroid 

 (idiopathic tetany), and certain obscure nervous diseases in adults, 

 such as paralysis agitans, may possibly also be associated with changes 

 in this gland. Chorea, epilepsy, and eclampsia have likewise been 

 thought to be associated with it. 



The parathyroid gland, besides influencing the nerve centers, has also 

 an influence on metabolism. The metabolic disturbances following parathy- 

 roidectomy are: (1) rapid emaciation and failure to grow; (2) a tendency 

 to the production of glycosuria, often detected by finding that the assimila- 

 tion limit for carbohydrate is lowered (page 652) ; and (3) most definitely 

 of all, an interference with calcium metabolism, as illustrated by the failure 

 of the teeth and bones to calcify properly. This interference with normal 

 metabolism led Kellogg and Voegtlin 81 to study the effect produced on 

 parathyroidectomized animals by the administration of calcium. It was 

 found that the symptoms were considerably ameliorated. These authors 

 concluded from their results that the essential cause of tetany is a 

 deficiency of calcium in the blood. It is possible however that the bene- 

 ficial action of calcium salts in this condition is that it decreases the 

 excitability of the nervous system, an action which it is known to 

 possess. 



