THE THYROID APPARATUS 65 



After the thyroid has been removed from dogs 3-5 weeks old, 

 the parathyroid bodies being left intact, the animals may be kept 

 alive for months or even years, provided that post-operative tetany 

 does not supervene. After about two months, the animals show a 

 considerable difference in size, as compared with control animals 

 of the same litter. After six months, this difference becomes so 

 marked that the control animals will weigh two or three times 

 as much as the thyroidectomized animals. 



I found that the constitutional changes were also very 

 noticeable.* The thyroidectomized animals are much smaller, the 

 legs are short and fragile, and the skull is rounded, with a 

 projecting infantile forehead. As a result, apparently, of 

 disproportion between the size of the viscera and that of the 

 skeleton, the abdomen appears to be very much distended. 

 Occasionally there is a peculiar deformity of the breast-bone. 

 It is remarkable that the mental apathy and impaired intelligence 

 which, according to v. Eiselsberg, is invariably displayed by 

 thyroidectomized sheep and goats, is absent in the case of young 

 dogs. This is the more remarkable in view of the fact that 

 spontaneous cretinism is known to occur in young dogs (v. 

 Wagner). Examination of the skeleton shows that all the bones, 

 and especially the hollow long bones, are remarkably fragile in 

 thyroidectomized dogs, while in the herbivora, on the other hand, 

 the bones are short, thick and heavy. The post-mortem 

 examination of my thyroidless dwarfed dogs revealed the per- 

 sistence of an exceptionally large thymus, where normally only 

 slight traces of this organ are found ; up to the second or third 

 year there was distinct hypertrophy of the hypophysis cerebri 

 with increase of colloid; a slight hypertrophy of the cortical part 

 of the suprarenals ; and a very noticeable hypoplasia of the sexual 

 glands. In one instance I found a very much hypertrophied 

 accessory thyroid gland embedded in the adipose tissue of the 

 aorta. The skin showed neither the clinical nor the histological 

 changes characteristic of myxcedema. Similar results have since 

 been obtained with dogs by Massaglia, and by Parhon and Gold- 

 stein with cats. The arrest in the growth of the skeleton and in 

 the development of the sexual organs is the typical and invariable 

 result of the absence of the thyroid function in both carnivora and 

 herbivora. 



The changes seen in older animals after thyroidectomy are, 

 as a general rule, much less clearly marked. They are principally 

 confined to changes in the metabolic processes, the clinical mani- 

 festations of which are : Loss of appetite, sluggish digestion, 

 increased emaciation, and, finally, cachexia thyropriva. 



Loss of intelligence is rarely seen. The disinclination for 



* Illustrations will be found in A. Biecll, " Innere Sekretion," Vorlesungen, 1902, 

 Vienna, 1903. Wiener Klinik, xxix, 1903. 



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