968 



SCIENCE. 



[N. S. Vol. V. No. 130. 



slowly developing changes are observed 

 corresponding to myxoedema. Hence, in 

 some animals thyroidectomy is followed by 

 such a marked disturbance of physiological 

 balance that death results very quickly, 

 while in others the development of symp- 

 toms is very slow, giving rise to chronic 

 effects which may endure for months. Evi- 

 dently, aside from the more acute and toxic 

 effects which may immediately follow the 

 operation, there are more gradual disturb- 

 ances of metabolism which eventually lead 

 to the complete breaking down of the ani- 

 mal. That the symptoms thus produced 

 are dependent upon the withdrawal from 

 the system of certain specific products is 

 evident from the fact that after extirpation 

 of the thyroidal tissue the mere feeding of 

 thyroid glands, or the subcutaneous and 

 intravenous injection of thyroid extracts, 

 sufSces to quickly dispel the myxoedemal 

 swellings, the rough thickened condition of 

 the skin, the muscular and mental apathy, 

 etc.* With dogs the convulsions which 

 follow extirpation of the thyroids are quickly 

 checked by the subcutaneous injection of 

 thyroid extracts. Experiments along these 

 lines with extracts of dead tissue have, as 

 you know, made it very evident that the 

 thyroid gland forms some one or more spe- 

 cific substances, the absence of which from 

 the body sooner or later renders life impos- 

 sible. Where, however, the animal, aa a 

 dog, is provided with accessory thyroids 

 the entire thyroid gland may be removed 

 without death resulting, providing one of 

 the parathyroids is left, but if both para- 

 thyroids are excised then 40 per cent, of 

 the thyroidal tissue proper must be left in 

 order to have the dog live.f Evidently, 



* See Kent : Thyroid extract after Thyroidectomy. 

 Proceed. Physiol. Soo ; Journal of Physiol. Vol. 15. 

 AlsoMeltzer: Ueber Myxodem. Centralbl. f. Physiol. 

 1894, p. 698. 



t Edmunds: Observations on the Tliyroid and Para- 

 thyroid of the Dog. Journal of Physiol. Vol. 22. 

 Proceed. Physiol. Soc. June 27, 1896. 



the thyroids and accessory thyroids have 

 more or less of a common function, the one 

 being able to fulfil the purpose of the other 

 to a certain degree; a fact which in itself 

 may be taken as evidence of the importance 

 of thyroidal tissue and the care exercised 

 by nature in preventing its complete sup- 

 pression. 



The very nature of the physiological re- 

 sults which follow the removal or accom- 

 pany the atrophy of the thyroidal tissue 

 suggests the formation of one or more toxic 

 substances to which the well marked symp- 

 toms are due ; substances which are either 

 not formed in the presence of thyroidal tis- 

 sue or else being formed are either neutra- 

 lized (physiologically) or decomposed and 

 rendered inert by substances furnished by 

 the thyroid gland. Such a view obviously 

 implies a difference in the character and 

 possibly in the extent of the metabolic 

 changes going on in the body, and we 

 maj^, therefore, advantageously consider the 

 character of our knowledge upon this sub- 

 ject. A careful study of the literature 

 shows quite clearly that certain definite 

 statements are justified. Thus, Leichten- 

 stern and Wendelstadt * found by feeding 

 thyroid glands to healthy obese individuals 

 that a marked loss of body-weight resulted. 

 Eoos,t experimenting with normal dogs, ob- 

 served that in feeding the gland substance 

 for several days there was a marked in- 

 crease in the excretion of nitrogen through 

 the urine, also of sodium chloride and of 

 phosphoric acid (P^ Oj) . On dogs with the 

 thyroids removed, this action was still more 

 marked, so far as the excretion of nitrogen 

 and chlorine was concerned, also in the loss 

 of body-weight and in the excretion of 

 water, but the excretion of phosphorus fell 

 behind the normal. Further, in an ex- 



* Ueber Myxcedem und Entfettungskuren mit 

 Schilddriisenfiitterung. Deutsch. med. Wochensohr. 

 1894. No. 50. 



t Loc. cit. 



