SOUTHERN CALIFORNIA. ACADEMY OF SCIENCES 75 
The lymphatics are represented in the brain by perivascular 
lymph channels. In this connection attention may be ealled 
te the peculiar neuroglia cells called ‘“‘pod asteroids.’’ These, 
which resemble the ordinary short-rayed gla cells in form, have 
from one to three short, fleshy, hollow processes which rest 
by a heavy expansion or “‘foot’’ upon the walls of the perivas- 
eular lymph channels. After traumatism or disease of the 
cerebral cortex, these cells are found to be swollen and filled 
with debris; the channeled processes also contain disintegrated 
nerve matter. The podasteroids seem, therefore, to act as ex- 
eretory organs, though this function has not yet been satisfac- 
torily demonstrated. 
It does not appear that blood leaving the brain differs from 
venous blood found elsewhere in the body. The cell body with 
its stroma, fibrils and hyaloplasm, the bodies of Nissl, the 
various structures of axon and hillock, of nucleus and nucle- 
olus, of karyoplasm and membrane, all are built from the water 
and oxygen, the various salts, albumins, globulins, and other 
compounds found in normal blood. The products of neurcne 
katabolicism include carbon dioxide, urea, some of the xanthins, 
cholesterin, lecithin and other compounds characteristic of 
katabolism everywhere. 
In addition to the foods needed by all cells, the neurone 
requires for its normal metabolism the products of the ductless 
elands—the thyroid, the pituitary body, the supra-renals, ete. 
Perhaps we may think of these, with Sajous, as oxidizing fer- 
ments. .According to Barker, these internal secretions are 
nutritional in their influences upon the neurone, that is, they 
may elaborate certain compounds essential to normal nerve 
nutrition, they may render inert some poisonous excreta of 
the neurone, or they may supply substances to the blood which 
perform this function. The symptoms of myxoedema, cretinism 
and acromegaly illustrate the grave effects of abnormal con- 
ditions of these glands upon neurone metabolism. 
Normal metabolism requires a certain amount of activity. 
For this, the neurone is dependent upon external stimulation. 
The retinal cells, for example, are dependent upon lght, the 
olfactory upon odor, and so forth. The sensory neurones of 
higher orders depend for their stimulation upon impulses 
arising from the peripheral sensory neurones. The association 
areas receive from the sensory neurones the impulses which, 
after re-arrangement, are sent out over the motor pathways. 
Ultimately, therefore, the activity and development of the 
whole nervous system is dependent upon the number and char- 
acter of the impulses sent in over the sensory neurones. 
