24 THYMUS AND PARATHYROID GLANDS 



manders, Ambystoma opacum; again each single individual after a 

 certain time came down with tetanic attacks. In 1917, the experi- 

 ments were repeated with the same result on both species. It is, 

 therefore, evident that the thymus gland contains a substance which 

 produces tetanic convulsions in the larvae of Ambystoma maculatum 

 and opacum. 



Tetanic Symptoms. 



The tetanic symptoms exhibited by salamander larvae fed with 

 thymus closely resemble the symptoms produced by parathyroid- 

 ectomy in mammals.^ The first attacks in the larvae are confined to 

 the hind portions of the body. In general, this part of the body suffers 

 more than any other during the entire tetanic period, and when the 

 acute attacks become less and less frequent and severe it is again the 

 hind portions of the body which alone are attacked. Within several 

 days after the onset of acute tetany the entire muscular system exhib- 

 its severe clonic convulsions. Each single attack begins at the tail 

 and spreads toward the head; the tremors are severest in the legs and 

 in the muscles of the lower jaw. During each attack the mouth is 

 thrown widely open. When the attack begins the animals are thrown 

 on one side. Besides the clonic convulsions a tonic spasm of the entire 

 body is observed ; the legs are stretched out and the body is bent with 

 its concavity towards the back. During the attack the animals dis- 

 charge much air and the vessels of the skin become very red. 



In the early stages of the disease the convulsions are induced only 

 upon stimulation which is best effected by removing the larvae from 

 the water, placing them on filter paper, and pinching the legs or the 

 tail slightly. Each attack lasts only a short time, the larvae recover- 

 ing after from 2 to 3 minutes. Later any attempt of the larvae to 

 swim or to snap at a piece of food suffices to induce an attack and 

 some individuals may float for several days on one side, being rigid 

 from tonic spasm. 



8 to 14 days after the first attack the hind legs begin to show 

 signs of a permanent tonic spasm; the legs are stretched backward 

 and become twisted around their longitudinal axis with the inner 

 surface pointing upward ; the feet follow this movement and finally 

 the fore legs undergo a similar change. 



3 See Biedl, i, 79 ff. 



