176 THE THYROID, THE THYMUS, AND THE ADRENALS. 



development was mainly physical. A considerable increase in 

 height was observed in all the cases, but the mental symptoms 

 ufere not improved." It seems evident that if, on the one 

 hand, the vast majority of cases of mentally weak children do 

 not possess thymus glands, and that, on the other, thyroid 

 extract will enhance growth of idiotic children (not mvx- 

 cedematous ones, i.e., cretins), the oxidation processes, stimu- 

 lated by the thyroid through its action on the adrenals, are 

 inadequate to alone bring on improvement of the mental 

 symptoms. Again, it becomes evident that it is upon the 

 thymus that the mental development depends, and, finally, 

 that it is to some agent which the thyroid gland does not 

 contain that this development is due. 



This enables us to eliminate iodine as the main active prin- 

 ciple of the thymus gland, and, our inquiry being disconnected 

 from the oxidation process through the evident inefficiency of 

 the thyroid to restore mental functions, we are led to seek for 

 a chemical body that will enhance cerebral nutrition. Can we 

 expect such an hypothetical agency, however, to concentrate 

 its effects upon the brain alone? This is hardly probable, 

 judging from analogy, and the nervous system at large must 

 also utilize it physiologically. Our field is therefore broadened, 

 since an agency connected with the nutrition of the brain 

 alone, or one playing the same role in respect to the entire 

 nervous system, may serve our needs. This is, to say the least, 

 fortunate, for the chemistry of brain- and nerve- matter is far 

 from well known, and even a good analysis i.e., one based 

 upon the more salient data available would be impossible 

 were the limits of the inquiry at all narrowed. 



Of the solid constituents of nerve- and brain- matter, 

 three stand out prominently: cholesterin, cerebrin, and lecithin. 

 Cholesterin, considered by Austin Flint, Jr., as a waste-product 

 of cerebral and nervous origin, though it represents one-half 

 of all the solids, shows no molecular constituent capable of 

 assisting us (C 26 H 44 0), the fact that the thyroid secretes a 

 specific agency being taken as standard; nor does cerebrin 

 (C 17 H 33 N0 3 ), though both this and the preceding body are 

 found in abundance in the cerebro-spinal axis and nerves. 



The italics are our own. 



