THYROIDS AND PARATHYROIDS 647 



appear, and increase in severity, until at length they culminate in 

 general spasmodic attacks. Even when the animal is at rest the 

 fore-legs tend to be flexed, while the hind-legs are extended, and this 

 attitude is exaggerated in the convulsions. In the later stages un- 

 consciousness is associated with the onset of the convulsions. Similar 

 results follow excision of the parathyroids alone in dogs. Although 

 the tetany is the most striking symptom, it is only one token of a 

 profound general disturbance of nutrition. The pulse-rate and the 

 rate of respiration are markedly increased. There is fever and pro- 

 fuse salivation, with dilatation of the stomach and duodenum, due 

 to the loss of muscular tonicity. In the intervals between attacks 

 the tonus returns to the normal. The secretion of the gastric 

 juice, pancreatic juice, and bile are interfered with (Carlson, etc.). 

 The excitability of the vaso-constrictor mechanism is said to be 

 increased. The exact significance of these symptoms is unknown. 

 It has been suggested that the loss of the parathyroid function is 

 in some way associated with an augmentation of the irritability of 

 the whole sympathetic system (Hoskins). The administration of 

 calcium completely relieves the symptoms, and by its use death may 

 be long or perhaps indefinitely postponed (W. G. MacCallum). The 

 mode of action of the calcium has not been made clear as yet. It 

 does not seem to be so efficacious in rabbits as in dogs (Arthus). 



A suggestive fact is the increased amount of guanidin, methyl and 

 dimethyl-guanidin in the urine of dogs after parathyroidectomy (Koch). 

 Recently the hypothesis has been put forward that the parathyroids 

 regulate the metabolism of guanidin in the body and by doing so, 

 probably exercise a controlling influence on the tone of the muscles. 

 In support of this, it is pointed out that in tetania parathyreopriva 

 there is a marked increase in the amount of guanidin and methyl- 

 guanidin in the blood, as well as in the urine. This is also true of the 

 urine of children suffering from the disease known as idiopathic tetany, 

 in which the parathyroids are supposed to be implicated (Paton, etal.). 

 Symptoms and metabolic changes like those in experimental and patho- 

 logical tetany are said to be caused by guanidin and methyl-guanidin. 



Thyroidectomy. The symptoms that follow removal of the 

 thyroid alone are perfectly different. The metabolic disturbance is 

 eventually, in most animals, not less far-reaching than that which 

 ensues when the parathyroids are alone excised. But it is far more 

 chronic, reveals itself by totally distinct changes, is not amenable 

 to calcium, and is completely corrected by the administration of 

 thyroid substance. While no animals which have been examined 

 survive the total removal of the paratrryroids, certain species 

 e.g., the goat are but slightly affected by thyroidectomy, and 

 survive indefinitely. In man, before the consequences of thyroid- 

 ectomy were known, the whole gland was not infrequently excised 

 for goitre. If the parathyroids happened also to be completely 

 involved in the operation, death quickly followed. But where only 



