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IOWA ACADEMY OF SCIENCES 
width. Cells from the adult are 9 micra in height and 11 micra in 
width. The contents of the cell in the young form are w'ell nigh 
■ unstainable at least by ordinary methods. The nucleus stains diffusely 
and a small amount of cytoplasm at the apex takes up stain hut the re- 
mainder of the cell remains clear save for a few' radiating lines of micro- 
sornes. The location of the nucleus in the one day rat is peripheral 
w'hile in the adult it is central. In the former it averages 7 micra from 
the base while in the latter it is only at a distance of 2 micra. As 
the rat grow'S older a gradual change in all these particulars takes place. 
The cells widen, begin to take up more stain, and the nucleus moves to- 
ward the center. By the seventh day the cells have assumed the adult 
type. 
These same changes in the epithelium after birth have been noted in 
the cat and rabbit, and doubtless they occur in other forms. The primi- 
tive cylindrical condition of the epithelial cells is evidently retained 
until extra-uterine life is well begun. Whether this means that the cells 
do not function until adult life cannot be said. It would indicate that 
their work could not be the same as in the adult. 
Thus far we have studied the plexus in what might be termed its 
resting stage. Careful examination shows that there are ahvays some 
ceils in any plexus that have the appearance of secretory phenomena, 
for many years there has been a suspicion that the choroid plexuses 
secreted or at least aided in the secretion of the cerebro-spinal fluid. 
But until recently the idea remained without much supporting evidence. 
Capelleti (1) in 1899 made use of a cerebro-spinal fistula to study the 
effect of drugs on the flow of the cerebro-spinal fluid. In 1902 Pettit 
and Girard (2) w'ent a step farther by administering drugs to animals 
and then removing the plexuses to And whether there w'ere any evidences 
of secretion in the epithelial cells. The writer has made experiments 
along the same line as these investigators. No claim is made for 
originality but the results may be of interest since in some cases other 
forms w'ere used for study. 
By cleaning aw'ay the musculature from the back of the neck a glass 
canula may be inserted through the dura into the fourth ventricle and 
the cerebro spinal fluid secured as it is secreted. Dogs were used for 
these experiments. In etherized dogs the insertion of the canula is 
followed by a rapid rush of fluid. This is due to the rapid secretion 
under the influence of the ether and a consequent accumulation of the 
fluid. The flow from the ether persists for about thirty minutes but 
gradually decreases. If 1% pilocarpine now be injected through the 
femoral vein the secretion becomes stronger and reaches a maximum of 
3 to 4 drops a minute. An injection of atropine wull now abolish the secre- 
tion entirely. 
Microscopic examination has been made of the plexuses of dogs and 
rabbits that had been under the influence of ether for 20 minutes, and 
also of rabbits, guinea pigs, and rats injected wuth muscarin. The latter 
drug w'as most useful when diluted to 1-500. 
Archiv. Ital de Biol. XXXVI. p. 299-302, 1901. 
(2) Pettit and Girard. Archiv. d’ Anat, Mic. tV. p. 213-264. 1902-1903, 
