Meek, Choroid Plexus. 301 



tion, we may quote some observations on the vesicular theory. 

 LuscHKA ('55), FiNDLAY ('qq), Studnicka ('oo) and Galeotti 

 ('97) have all observed small globules within the epithelial cells 

 of the plexus, and on the free surface of the plexus itself. These 

 they have taken as evidence of the vesicular secretion by the 

 epithelial cells. Pettit and Girard ('02-03) call attention to 

 the fact that these globules increase in number with the time the 

 tissue remains unfixed, and also with the slowness of fixation. 

 These globules are analogous to the sarcode globules which are 

 known to be due to post-mortem changes. These globules have 

 been reported for fresh tissue, but they must have been due to 

 mechanical injury. If any one will crush a fresh plexus under the 

 microscope, he can see these structures form before his eyes. It 

 would seem that in the choroid plexuses fatty droplets may be 

 extruded in a way prescribed by the vesicular theory, but the nor- 

 mal secretion passes through the marginal zone in another way, 

 possibly by some kind of canaliculi. 



The chemical composition of the cerebro-spinal fluid has often 

 been advanced as a proof of its being a secretion and not a transu- 

 date. Halliburton ('89) has shown that it is peculiar and dif- 

 ferent from the lymph and blood serum in its proteids and in the 

 presence of a reducing substance. The proteids are a globulin 

 coagulating at 75° C. and albumoses and peptones. The reduc- 

 ing substance Halliburton identified as pyrocatechin, but this 

 identification does not seem to have been confirmed, later investi- 

 gators reporting the presence of glucose. In the amount of sodium 

 and potassium salts, there is but little difference from the blood 

 serum. 



The function of the cerebro-spinal fluid and its circulation are 

 of interest, but related only indirectly to our subject, so we shall 

 discuss them very briefly. The general idea has always been that 

 the fluid is a nutritive solution to nourish the nerve cells with 

 which it may come in contact. Spina ('01) has shown that absorp- 

 tion of the cerebro-spinal fluid may take place, since fuchsin 

 injected into the subdural spaces appears in the jugular vein. He 

 concludes that the absorption is proportional to the pressure 

 exerted on the fluid. The plexuses themselves, however, can 

 scarcely be resorptive organs, for the blood pressure in the capil- 

 laries is too great to admit of it. Still it is not inconsistent to 

 believe that the cerebro-spinal fluid may be absorbed to some 



