THE THYROID AND PARATHYROID BODIES 



953 



stable substances and may be subjected to ordinary degrees of heat 

 without losing their function, a fact which sharply differentiates them 

 from the ferments and enzymes. To be sure, both these agents are 

 cellular products, but while the autacoids are destructible and their 

 function is restricted to the domain of the body, the enzymes are not 

 limited in this way. Moreover, they are resistant, and are not changed 

 during the processes evoked by them. 



Any other classification of the autacoids meets with the difficulty 

 that they act upon specific groups of cells and that the effect produced 

 by them is usually rather vague in character. Thus, while the action 

 of adrenin is quite obvious, other internal secretions, for example, 

 those of the thyroids and thymus, possess a general metabolic function 

 which it is difficult to analyze. Gley, ^ however, suggests the following 

 classification : 



(a) Nutritive 



(6) Harmozones 



(Glycose, liver, 

 Fat, intestinal mucosa, 

 Albumins of blood, intestinal mucosa and blood. 



1. Substances effecting / sugar metabolism, pancreas, 



nutritive changes 

 2. Substances helping 

 to maintain int. me- 

 dium 



I sugar mobilization, adrenals, 

 \ antithrombin, liver, 



3. Morphogenetic 



(c) Hormones 



testicles, 

 ovaries, 

 thyroid, 

 hypophysis, 

 . thymus. 



i r^u • 1 / activating the trypsin, spleen, 



'"^^"'''^^n catabolic, thyroid, 

 I ( secretin, duodenum 



I Physiological \ adrenin, adrenals, 



I galactogogue, placenta. 



.js -P, , / Carbon dioxid, muscles and glands, 



(d)Parhormones|^^^^ 1-^^^ 



An inspection of this table must show immediately that this clas- 

 sification is by no means sufficiently embracing to include all of the 

 internal secretions in their proper relation to one another and hence, 

 it may be permissible to arrange them in accordance with their location 

 rather than their function. In the first place, it is to be noted that 

 these secretions originate in the so-called endocrine organs (Greek epdov 

 within, and Kplpo) to separate), including the thyroids, parathyroids, 

 thymus, duodenum, Hver, pancreas, adrenals, pineal gland, pituitary 

 body, placenta, choroid plexus, and the testes and ovaries. Every one 

 of these glands presents at least three of the characteristics ordinarily 

 assigned to an internal secretory structure, namely: (a) the cells com- 

 posing them are usually arranged in the form of acini, and embrace a 

 certain amount of granular and other material from which the secretion 



1 The Internal Secretions, translated by Fishberg, Hober, New York, 1917. 



