48 Herring 



Scluifer (16), in summing up the evidence of the action of the thyroid 

 upon the suprarenals, states that " it may be assumed that the secretion 

 of the thyroid in exophthalmic goitre acts as a direct stimulant to the 

 suprarenal capsules, causing them to yield adrenalin to the blood in larger 

 (quantity ; a result which is also obtained by thyroid feeding." 



That the suprarenals readily give off adrenalin into the blood has been 

 frequently shown. Elliott (7) found such to occur as the result of the 

 administration of anajsthetics. Cannon and de la Paz (3) detected a 

 rise of adrenalin in the blood following upon emotional influences. 

 Cannon and Hoskins (4) showed an increase in the blood of cats as the 

 result of asphyxia and stimulation of the sciatic nerve. The amount of 

 adrenalin in the blood is therefore liable to vary. An increase in the 

 blood does not necessarily indicate an increase of adrenalin in the body. 

 A better index of any change in the adrenalin content of the body is 

 furnished by an estimation of the amount in the suprarenal capsules and 

 chromaphil tissue. IMoreover, measurements of adrenalin in the blood are 

 not very satisfactory, partly because of the minute quantity present, and 

 partly because of the methods employed. Schafer (op. cit.) utters tlie 

 caution that most of the physiological tests which have been used for 

 measuring adrenalin in the blood would also be given by pituitrine. 



In the following experiments the weights of the suprarenals of normal 

 and thyroid-fed animals are recorded and compared. The adrenalin of 

 the suprarenals is estimated by Folin's micro-chemical method. 



Procedure. 



The animals used are white rats. These were selected partly because 

 of their small size and the convenience with which they can be observed 

 and fed, but also because their response to small measured doses of th^'^roid 

 has already been recorded by Hewitt (12). A further advantage in their 

 use lies in the fact that many details, more especially as regards age, size, 

 and weight of body and organs of the white rat, have been compiled by 

 Donaldson (6) in the Memoirs of the Wistar Institute. The rats selected 

 were all males. The female rat has relatively larger suprarenals than the 

 male, the diti'erence tending to increase as age advances (Donaldson). 

 The animals reserved for thyroid-feeding were of various ages, but were 

 mostly young adults. A like number of animals of as near the same ages 

 as possible were kept as controls. Both sets were given a supply of bread 

 and milk more than necessary for their daily requirements. The one set 

 received each a daily addition of 05 grm. fresh ox thyroid finely minced 

 and mixed with the bread and milk. The amount of thyroid was fixed 

 at 0-5 grm. fresh gland because it is about the upper limit of the dose 

 which may be given without producing loss of weight of the animal. 

 The feeding was continued for from 20 to 30 days. Each thyroid-fed 

 animal was kept in a separate metabolism cage so as to ensure that it 



