THE THYROID AND PARATHYROID GLANDS 801 



eral, however, it has been found that if more than two of the four 

 parathyroids be removed, very definite and pronounced nervous symp- 

 toms soon supervene and if all four glands be removed, a quickly fatal 

 result is inevitable. The most acute symptoms are exhibited by the 

 carnivora. They may not be apparent for a day or two after the opera- 

 tion, although during the period the animal is in a depressed state, re- 

 fusing food and losing weight rapidly. The muscles are also more or less 

 stiff during this stage. When more definite symptoms appear, they con- 

 sist of a marked abnormality of muscular contraction, leading to the 

 occurrence of fibrillar contractions, or tremors and, later, to cramp-like 

 and clonic contractions. When spontaneous movements are made, a 

 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 and rapid pulse. In addition to the clonic seizures, 

 there appears a tonic contraction of the extensor muscles of the limbs and 

 in a certain percentage of dogs (but not of cats) spasm of the adductor 

 muscles of the larynx (laryngismus stridulus) occurs. In this latter con- 

 dition owing to the consequent narrowing of the rima glottidis the res- 

 pirations are noisy, difficult and high pitched in tone. 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 tis- 

 sue has been left for example, one of the four lobes the symptoms may 

 not appear except under conditions of special strain to the animal econ- 

 omy, such as pregnancy or improper diet. Thus, .in a bitch from which 

 three of the four glands had been removed, no symptoms of tetany oc- 

 curred 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 con- 

 dition than one of vegetables or milk. 



Injury or Disease of the Parathyroids in 



Tetania parathyreopriva, as the condition described in the foregoing 

 paragraph is called, may become developed also in man as the result 

 of surgical removal of the parathyroids. This was a common enough 

 sequela to operations for goiter a few years ago, before the significance 

 of these bodies was recognized or, indeed, even their existence known. 

 It was the result of accident rather than of design, were the parathyroids 

 not removed along with the thyroid. A similar condition (idiopathic 

 tetany) occurs spontaneously, in children more particularly, but also in 

 adults when it may be associated with gastrointestinal disorders, infec- 

 tious diseases, or pregnancy. The clinical phenomena resemble closely 



