4 i6 SCIENCE PROGRESS 



physiology. One of the most generally accepted among recent 

 views may be stated as follows : As regards vital importance, 

 the function of the thyroid gland is subsidiary to that of the 

 parathyroids. Removal of all the parathyroids from an animal, 

 even if the thyroid be left intact, invariably proves fatal within 

 a short time, and this with typical nervous symptoms described 

 under the name of u tetany." Removal of the thyroid, on the 

 other hand, gives rise to an entirely different train of S3'mptoms, 

 stated to be those of "post-operative" myxoedema. This view 

 assumes first of all that thyroid and parathyroid are separate 

 organs with totally distinct functions. It further assumes that 

 myxcedema in the human subject and post-operative myxcedema 

 in animals are due to thyroid insufficiency, while the nervous 

 symptoms which frequently occur after operations on animals are 

 due to parathyroid insufficiency. 



Unfortunately this theory, though devoid of complexity, is 

 not supported by the evidence at our disposal. The extreme 

 importance to life of the parathyroids is more than doubtful. 

 Kishi (18) found that dogs and cats often die after operations 

 on the thyroid, although the parathyroids be left behind. The 

 present writer, in conjunction with W. A. Jolly (19), found 

 further that removal of all four parathyroids was not necessarily 

 fatal. We were furthermore unable to confirm some other 

 statements which are commonly accepted. It cannot be truly 

 said that either thyroids or parathyroids are essential for 

 life, since it is frequently possible to remove either or both 

 without causing death. The functional importance of the glands 

 appears to differ very widely in different classes of animals. 

 Rats and guinea-pigs do not seem to suffer at all as the result of 

 extirpation. Monkeys only show transient nervous symptoms, 

 and even these are sometimes wanting. Dogs and cats frequently, 

 but by no means invariably, suffer severely and die. In foxes 

 symptoms come on with remarkable rapidity, and death is 

 correspondingly early. In no animal were we able to induce 

 symptoms resembling myxcedema. Myxcedema, and probably 

 also cretinism, must then, in our view, be due to causes more 

 complex than simple thyroid insufficiency. When the thyroid 

 is removed the parathyroids appear capable of functionally 

 replacing it to a certain extent, and their histological structure 

 changes accordingly. 



Perhaps the point of most general interest in the above results 



