Kffect of Tliyioid-Fcediii*,' on ilu- Suprarenals 55 



naked-eye exainination ilie cortex of the suprarenals appears enlar;,'ed 

 in tlje thyroid-fed rats, and it is possible that the cortex undergoes a 

 relatively greater hypertrophy than {]}<■ medulla. 



In a previous paper the author gave the average adrenalin content of 

 the suprarenals per kg. body-weight as 0400 nig. in tlie rabbit and 

 0-22i» nig. in the cat. The adrenalin content of the rat more nearly 

 approaches that of the rabbit than that of the cat. Vjeing 0034 mg. per 

 100 grm. body-weight. 



The Adrenalin Content of Ketkoperitoneal Ti.ssie. 



Attempts were made to estimate by Folin'.s method the adrenalin in 

 extracts of retroperitoneal tissue in the first six animals both of the control 

 and thyroid-fed groups. The colour ])roduced, however, was generally 

 too weak for .satisfactoiy measurement. Swale Vincent (17) was unable 

 to find any chromaphil bodies in the rat. Fulk and Macleod (10) have 

 recently athrined the presence of retroperitoneal chromaphil tissue in the 

 rat. and find that its extracts act similarly to weak solutions of adrenalin 

 on intestinal muscle. The author, like Swale Vincent, has not been 

 able to find any definite chromaphil bodies by histological metliods. 

 Extracts of the retroperitoneal tissue, when carefully prepared so as to 

 precipitate the proteins, give a variable response to Folin's reagent. 

 Sometimes the colour produced is very slight, at other times i|uite measure- 

 able. A slight reaction to Folin's reagent does not necessarily indicate the 

 presence of adrenalin. The stronger reaction, when present, is probably 

 due to the inclusion in the retroperitoneal tissue of accessory suprarenals. 

 They are not uncommon in the rat, and are often very minute. It is often 

 impossible to distinguish them by anything but microscopical observation. 



The accessory suprarenals appear to be larger, and their chromaphil 

 cells more abundant in rats which have been thyroid-fed. In several of 

 the animals recorded in Table II. the amount of adrenalin in the accessory 

 suprarenals must have been quite appreciable. This was especially the 

 case in rat No. 13, in which the suprarenals contained 0*138 mg. of 

 adrenalin. Subsequent investigation of the retroperitoneal tissue of this 

 animal after fixation in bichromate of potash solution showed the existence 

 of three small accessory suprarenals each containing chromaphil cells. 

 The total adrenalin content of this animal would have been larger if these 

 bodies had been included. 



While no definite figures can be given, the author believes that there 

 is evidence to show that where accessory suprarenals are present they 

 participate with the suprarenals in the enlargement and in the increase 

 of adrenalin content resulting from thyroid-feeding. 



Mortality under Small Doses of Thyroid. 

 Reference has been made to the frequency of sudden death occurring 

 in rats while under the influence of small doses of thyroid. This has 



