THE PHYSIOLOGY OF THE NEURON. 531 



nerve-fiber": both ascribable, it now seems likely, to the one 

 organ, the posterior pituitary body. 



To establish the functions of the posterior pituitary within 

 its proper physiological limits, however, it is necessary to as- 

 certain how nervous elements in general and neurons in par- 

 ticular are nourished, since it is upon the degree of perfection 

 with which the nutritive processes are carried on by the blood 

 that the functional integrity of these structures depends. 



The fact that a general nutritional process prevails, of 

 which the suprarenal system is the primary motive agency, we 

 have shown; but it finds further support in the following 

 statements of Professor Barker's which, of course, but em- 

 phasize a generally known fact that, "in the absence of sub- 

 stances in the body derived from the thyroid gland, the nervous 

 system undergoes very important and serious metabolic modi- 

 fications, evidenced by the remarkable nervous and mental 

 phenomena with which all are now familiar. On restoring 

 these substances to the body by the administration of a thyroid 

 extract the symptoms may sometimes be made to disappear. 

 It is likely, however, that the neurons find their staple foods 

 in the main nutritive constituents of the blood as derived from 

 the food digested in the stomach and intestines and purified 

 by the lymph-glands and liver." 



We have, we believe, satisfactorily shown that the thy- 

 roid secretion sustained the activity of the anterior pituitary 

 body, and therefore of the entire suprarenal system, by pour- 

 ing its secretion thyro-iodine perhaps into the blood. The 

 functions of the digestive organs we have also reviewed. 

 Among the latter, however, are two upon which we laid con- 

 siderable stress, i.e., the spleen and pancreas, and we called 

 attention to the great importance of trypsin the spleno- 

 pancreatic ferment in the conversion of albuminoid sub- 

 stances, and especially of their toxic derivatives, into benign 

 products. These albuminoid substances, we have seen, then 

 pass through the liver, and, after traversing the cardio-pulmo- 

 nary circuit, are distributed broadcast throughout the organism. 

 There is a feature which we kept in abeyance, however, 

 though a well-known one, since at the time its true weight 

 would not have asserted itself: i.e., the fact that albuminoids 



34 



