146 BIOLOGICAL PHYSICS 



interpolated tissues, as shown by the common presence 

 of "excretory" material and function, which determines 

 consequent likeness in such pathological conditions as 

 adenoids of the nasal passages, enlargements of the 

 pharyngeal mucosa, and haemorrhoidal developments of 

 the post-rectal and anal parts. All which seems to us to 

 prove, what we may regard as axiomatic, that the operation 

 of like developmental factors on like, or intimately related, 

 organic materials results in the evolvement of like, or very 

 similar, developmental products, or structures, and hence 

 the great sameness which characterises the early condition 

 of the anteriorly united, and posteriorly separated, parts of 

 the neuro-enteric canal as to their textural conditions and 

 functional role ; hence, also the occurrence of such a thing 

 as the retention of a once common embryonic function, as 

 a still operative survival, in after life, such as is seen in the 

 secretion, or excretion, of peptone by the pio-meningeal 

 textures of the cerebrum and cord. 



These drainage areas are determined by anatomical and 

 histological necessities, due to the topographical disposition 

 and relative position of the textural divisions of the central 

 nervous system, and the system of drainage is determined 

 by the prevailing nature as to consistence of the drainage 

 material, and the outlet conditions best available and most 

 favourable to the operation of the existent local physio- 

 logical hydrostatics and dynamics ; the principal illustration 

 of which we might adduce as, what may be called, the 

 "cloaca major" of the central drainage system of the 

 cerebrum, or the infundibulo-pituitary apparatus, which 

 receives the residual and waste products of the great body 

 of cerebral material emanating from the mid- and hind- 

 brain, and excretes it on the surface of that continually 

 open, generally moist, and constantly swept, glosso- 

 pharyngeal cavity, or highway, situated at the commence- 

 ment of the gastro-intestinal or alimentary canal, where it 

 becomes, no doubt, a factor in the process of the 

 functional work of that canal of no mean importance, as 

 becomes, at once, apparent when any local pharyngeo-oral 

 obstruction to its physiological fulfilment takes place. 



The great cranial outlet, the foramen magnum, allows 

 of the free outflow of surplus cerebro-cerebellar lymph 



