THE THYMUS GLAND AND THE ADRENALS. 171 



THE THYMUS GLAND AND THE ADRENALS. 



If the conclusions just recorded as to the relationship 

 between the thyroid gland and the adrenals are sound, there 

 is considerable analogy between the effects of thymus on the 

 organism and those of the thyroid. Svehla's 40 well-known 

 experiments add further evidence to that submitted to the 

 effect that the thyroid gland only assumes its functions at 

 birth, extract of foetal thyroid having proven inert, while ex- 

 tract obtained from the thyroids of infants during the ^ first 

 month of life was effective. Precisely in the same manner did 

 thymus extract behave: foetal-thymus extract produced no ef- 

 fect, while that obtained from the thymus glands of infants in 

 the first month caused increase in the frequency of the pulse 

 and lessened blood-pressure. Further proof of the solidity of 

 the views herein advanced is also shown by his conclusions 

 based on experimental evidence that "among children of 

 the same age the thymus extract is the strongest; less so the 

 thyroid; and still less the adrenal. In adults, however, the 

 adrenal outstrips both other glands." The influence of this 

 suprarenal inadequacy is an important factor, we have seen, 

 in the predilection of children for infectious diseases. 



Svehla refers to "increased frequency of the pulse and 

 lessened blood-pressure' 5 as the prominent effects of thymus 

 extract: evidence, if its action corresponds to that of thyroid, 

 that a toxic dose had been administered to the experimental 

 animal This is confirmed by the fact that other typical symp- 

 toms were present: i.e.. muscular weakness, dyspnoea, and gen- 

 eral collapse, a condition from which the animals could be 

 saved by the timely administration of thymus extract, which 

 promptly restored the normal vascular pressure. The simi- 

 larity between the physiological actions of thyroid and thymus 

 as suprarenal stimulants is further shown by the experiments 

 of Isaac Ott 41 in rabbits. In these animals powdered thymus 

 caused the pulse to increase its rate and the blood-pressure 

 momentarily to rise, but soon to fall considerably: a suggestive 

 sequence of events. In another animal he found that the thy- 

 mus caused the respiration to increase and that section of the 



*o Svehla: Archiv fur exper. Pathologic, Bd. xliii. 

 Isaac Ott: Medical Bulletin, May, 1898. 



