THE THYROID APPARATUS 41 



case of old animals, the extirpation of all four parathyroids is 

 not followed by tetany. Haberfeld and Schilder found that if, 

 in such cases, the thymus and the accessory parathyroids em- 

 bedded in it were also extirpated, fatal tetany followed. It is 

 worthy of notice, however, that a proportion of animals continue 

 to live, even after removal of all the parathyroid glands. 



Christiani (1893) produced tetany in the rat by extirpation 

 of the entire thyroid apparatus. The results of destroying the 

 parathyroids by cauterization are minutely described by Erdheim, 

 who distinguishes between four degrees of tetany in rats. The 

 lightest form is shown by a rapid tremor of the extremities, 

 accompanied by single coarser spasms when the animal is lifted 

 from the ground. A more severe form consists in spontaneous 

 clonic contractions, trembling of the extremities, twitching in 

 the region supplied by the facial nerve, and quivering in nearly 

 all the muscles of the body. The third degree manifests itself 

 in tonic convulsions, which may be artificially provoked by 

 ligaturing the extremities, but which also occur spontaneously ; 

 the animals walk with the feet doubled up and there are tetanic 

 spasm in the muscles of the back and the extremities. The 

 severest form is characterized by epileptiform seizures, or by an 

 epileptic state lasting several hours. As a general rule the tetany 

 of rats is chronic in character and is accompanied by trophic 

 disturbances, to which we shall have occasion to refer later. 



The parathyroid tetany of mice, as described by Pfeiffer and 

 Meyer, is characterized by two stages. After a latent period of 

 twelve to tw T enty-four hours, there are attacks of clonic convulsion 

 alternating with tonic rigidity. The second stage is characterized 

 by an extreme motor restlessness, ataxia, and tonic rigidity; 

 somnolence follows, in which the animal slowly passes away. 



Parathyroidectomy of goats, according to Christens, is fol- 

 lowed by violent tetany. He finds, and his experiments are 

 confirmed by my own, that similar effects are produced by 

 extirpation of the thyroid and the superior parathyroids. 



Horsley observed that extirpation of the thyroid apparatus 

 of apes was in some cases followed by acute tetany. He believes 

 that the acute nervous after-symptoms appear only in young 

 animals when kept in a cold place. Horsley and others (Munk, 

 Langhans, Murray, W. Edmunds, Kocher, v. Eiselsberg, Capo- 

 bianco, Mazzioti) are of the opinion that a fatal termination is 

 less frequent than in the case of the carnivore, and that the 

 condition frequently passes into a stage of chronic cachexia with 

 extreme apathy. After extirpation of the four parathyroids, I 

 found that there was increased nervous irritability, fibrillary 

 twitchings, and finally, there were tetanic seizures and a fatal 

 termination. Pineles describes a case in which the symptoms 

 were similar, but the condition ran a more chronic course. 



Doyon and Jouty produced a typical tetany in birds by cauteri- 



