THE THYROID APPARATUS 43 



pregnant animals has been frequently described. It has been 

 proved, moreover (Adler and Thaler) that when animals, which 

 appear perfectly sound after the removal of two or three para- 

 thyroids become pregnant, pregnancy is heralded by an outbreak 

 of tetany. Fromme provoked tetany in such animals by injecting 

 them with placental extract. Rudinger sho\ved that a passing 

 tetany may be produced in cats from which the external para- 

 thyroids have been removed, by the introduction of certain toxins 

 (atropin, calomel, morphine, ergQtin, tuberculin), and by pro- 

 found ether anaesthesia. The assumption is that, in these cases, 

 a relative parathyroid insufficiency is latent and that any metabolic 

 derangement causes the symptoms of tetany to appear. 



In addition to the nervous symptoms, every acute tetany is 

 accompanied by secondary signs, such as shaggy appearance of 

 the coat; falling of the hair; eczema; and extreme emaciation. 

 These manifestations become more pronounced the longer the 

 animal lives after operation. Similar conditions are seen in 

 rabbits. If tetany does not develop after partial parathyroidec- 

 tomy, and if the animals continue to live, the nutritional con- 

 dition of all such animals is more or less seriously disturbed. 



Tetany in rats is strikingly chronic in character. The animals 

 in Erdheim's experiments survived from fifty-four to 162 days, 

 and invariably showed changes in the teeth. Between the sixth 

 and tenth w-eeks, opaque white spots appear upon the enamel of 

 the anterior surfaces of the upper and under incisors and these 

 move upwards from the base to the apex. These spots are cir- 

 cumscribed defects in the enamel, which may scale off and cause 

 the tooth to break. The upper incisors grow again quickly after 

 fracture, but fracture of the lower ones is frequently followed by 

 necrosing ulcers. As the changes in the teeth prevent the animal 

 taking a sufficiency of nourishment, extreme inanition and 

 cachexia follow. Histological examination of the teeth shows 

 that the trophic disturbances appear very soon after removal of 

 the parathyroids, and that they result from imperfect calcification 

 of the dentine together with hypoplasia of the enamel. 



Erdheim's observations are confirmed by Pfeiffer and Meyer 

 and by Iselin. Iselin also describes disturbances of the processes 

 of grow r th in the bones of speckled mice after removal of the 

 parathyroids. He found that in young animals there was com- 

 plete arrest of growth, unaccompanied, however, by secondary 

 bony deformity. 



Erdheim saw cataract in a rat with chronic tetany and he 

 regards this as a symptom of trophic disturbance. Albuminuria, 

 which was first observed in the tetany of animals by Pfeiffer and 

 Meyer, is an almost constant finding. Massaglia considers the 

 nephritis and albuminuria to be symptoms of an auto-intoxication 

 consequent upon parathyroidectomy. 



Iselin's account of the effects of the parathyroidectomy of 



