The endocrine organs : an introduction to the study of internal secretion / by Sir Edward A. Schäfer.

  • Edward Albert Sharpey-Schäfer
Date:
1916
Catalogue details

Licence: In copyright

Credit: The endocrine organs : an introduction to the study of internal secretion / by Sir Edward A. Schäfer. Source: Wellcome Collection.

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    of the blood-vessels and inhibition of that of the intestines. But in both cases the action may be regarded as that of a hormone or exciting agent, for both effects are produced by stimulation of the end substance of the sympathetic nerves. In extreme dilution (1 to several millions) in mammals, and in a less dilute form in birds, adrenalin is said to cause inhibition instead of contraction of the muscle of the blood-vessels. But this again may be produced by excitation of inhibitory nerve fibres by the more dilute solution, and if so, the action would still be hormonic. Nevertheless, the possibility of the same autacoid substance acting under some circumstances as a hormone or excitant, and under other circumstances as a chalone or depressant, must be borne in mind. This, indeed, serves to illustrate the drug-like nature of these principles, for such inversion of action under difference of circumstance is known to occur with some drugs. Noel Paton (Regulators of Metabolism, 1913) takes a view of the action of the principles of the internal secretions different from that usually adopted. He regards them as playing the same sort of part in the metabolism of the various organs they influence as Sydney Ringer showed to be the case with the salts of blood in maintaining the activity of the heart. “ A certain minimum amount of each seems to be essential, and some proportion between the amounts of each must be main¬ tained if the metabolism is to continue in its normal course. ... It seems to me that such a conception is more in accordance with the facts which we possess than that of a series of hormones or excitors directly calling forth the activity of the various tissues.” Groupings of the Chief Endocrine Glands Most of the purely endocrine glands can be grouped under the three main heads of thyro-parathyroid apparatus, suprarenals, and pituitary. It is noteworthy with regard to these groups that each of the organs forming the group is compounded of two distinct but usually closely inter- grown parts. Thus the thyro-parathyroid group is composed of thyroid proper and parathyroids; the suprarenal of cortical and medullary portions • the pituitary of epithelial and epithelio-neural parts. And in each case the functions of the two portions, so far as is known, appear to be in no way similar, difficult as it is to believe that tissues so closely connected anatomically should have no sort of functional connexion. The close anatomical connexion is, however, sometimes absent, as with those para¬ thyroids which are altogether detached from the thyroid, and as with the paired bodies and the interrenal body of Elasmobranch fishes. A close anatomical relationship without any apparent functional bearing is, how¬ ever, not without examples in other organs, e.g. in the frog there exists a very intimate anatomical connexion of the suprarenal with the kidney, although there is no particular reason to believe that any special functional relationship obtains between the two. It is further noticeable that in each of the above groups one of the two parts has a more evident, and in a sense a more active, function than the other. Thus the removal of the parathyroids occasions symptoms which are far more acute than those produced by the corresponding operation on
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