1886.] 



On the Function of the Thyroid Gland. 



9 



pressed the thyroid tremors just as voluntary movements do. Another 

 evidence of the changes in the cortex is the frequency with which 

 continuous stimulation will evoke the appearance of clonic spasms on 

 the original tetanic curve, the latter not being followed by epilepsy 

 when the current is shut off. 



(b.) Effect on the spinal cord. The tetanus obtained by stimulating 

 the spinal cord like that of the cortex rises slowly to the highest point, 

 and then steadily falls towards the abscissa although the stimulation 

 is maintained, and when the current is shut off the muscle completely 

 relaxes, having absolutely lost its tone, and this tonic paralysis is not 

 recovered from for ten to fifteen seconds. Stimulation of the spinal cord 

 to fatigue, after some time has elapsed so as to produce exhaustion of 

 the preliminary tetanus, evokes a tremor of eight to ten per second. 



Tracings from an old animal (cat) which had survived the operation 

 some months, and also from a dog, in which case the symptoms had 

 been very severe for some days, exhibited only a very feeble tetanus 

 in the former instance, and no reaction at all in the latter ; this being 

 the ultimate state of depression of function which the nerve-centres 

 had arrived to. 



(3.) I have thought it as well to add to the anatomical and physio- 

 logical proofs I gave last year of the thyroid gland being a hsema- 

 poietic structure by counting the number of corpuscles in the blood 

 of the thyroid artery and vein respectively. After discounting any 

 possible alteration in the relative number of the corpuscles in the two 

 vessels by changes in the fluid constituent of the blood which may 

 have happened in the gland, the much greater number of corpuscles 

 in the vein ( + 7 per cent.) confirms the deductions drawn from my 

 previous observations. 



To sum up, the functions of the thyroid gland appears to me to be 

 two-fold as already suggested, viz. r (I) Control of mucin metabolism, 

 (2) Hsemapoiesis. The metabolic processes in the body may be 

 regarded broadly as resulting in Construction and Destruction. The 

 products of destruction are the waste products of tissue change, and 

 being, as such, harmful to the organism, are cast out by the excretory 

 organ. It appears to me that the thyroid gland aids in excretion of 

 mucinoid substances or their precursors, not of course by excretion 

 properly speaking, that is, casting them out from the body, but by 

 metamorphosing them into some other form which is useful to the 

 system. That this process, whatever it is, is of vital importance to 

 the young mammal (seeing that interference with it causes death in a 

 few days) is obvious, and such as it is the loss of it is distinctly con- 

 nected with the appearances of the diseases known as myxcedema, 

 cretinism, and senile degeneration. Finally, this defect in the circle 

 of metabolism determines the appearance of so-called functional 

 disorders of the nervous system. 



