8 The Endocrine Organs 



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the thyroid. And extracts of the medullary substance of the adrenals and 

 of the posterior or epithelio-neural part of the pituitary have an immediate 

 and striking effect on various tissues and organs when injected into the 

 blood-vessels, whilst similar extracts of the cortical substance of the adrenals 

 or of the anterior or epithelial part of the pituitary are without any 

 immediate action. There is, however, in the case of the thyroid, direct 

 experimental as well as clinical evidence, and, in the case of the suprarenal 

 capsules and pituitary, the testimony of much clinical observation, to furnish 

 reason for the belief that the parts of these glands which at first sight 

 appear less active may exercise, if a slower, yet a no less potent influence 

 upon the organism than the portions the activity of which can be more 

 immediately demonstrated. 



Methods of Determining the Functions of the Endocrine Organs 



Two general methods are employed for this purpose, the one being 

 the observation of the changes which result from partial or complete 

 surgical removal of the organ in man and animals, or its destruction by 

 disease ; the other, observation of the changes which result from the ad- 

 ministration of watery or saline extracts prepared from the organ. As 

 has been already stated, the active principles of the endocrine glands are 

 j ! not destroyed by boiling with water or with Ringer's solution, at least for 

 a short time. Advantage is taken of this to prepare extracts which are 

 free or almost free from protein or nucleo-protein, since the introduction 

 of these substances into the blood might tend to mask the effect of the 

 autacoid which is being tested. Solutions obtained in this way may be 

 kept, after sterilisation, in hermetically sealed receptacles almost indefinitely. 

 Preserved in the dry condition the autacoids also appear to undergo no 

 diminution of their activity. In these particulars animal autacoids re- 

 semble extracts of plants containing active medicinal principles of an 

 organic nature, with the action of which, as has already been indicated, 

 the effects they produce bear a close comparison. 



As with drugs, the extracts can be administered by the mouth, or by 

 subcutaneous, or intramuscular, or intraserous, or intravenous injection. Or 

 isolated organs and tissues may be perfused with or immersed in the extract 

 the action of which is to be examined. The intravenous method was first 

 employed by Oliver and myself to investigate the physiological action of 

 such extracts in 1894, and led immediately to the discovery of the active 

 principles of the suprarenal capsules and the pituitary body. 



Administration by the Mouth. — This is well known to be effective in 

 the case of the thyroid, and the fact is taken advantage of in cases of hypo- 

 thyroidism such as occurs in endemic goitre, cretinism, and myxoedema. 

 On the other hand, thyroid juice or the substance of the gland given freely 

 with the food in normal individuals produces symptoms which are inter- 

 preted as due to excess of the thyroid autacoids in the blood. With smaller 



