of tllc cbf~it hcliurlt is ;L c+ytoj)lasmic. t~(~t\vorl<. f + ' r c ( j ~ ~ ( ~ ~ l t l ~
0111)
the hasal
~ncmbl.t~~lc. rcl~lt~itis of' the origi~li~l litli~lg of the trtbtrle. There is thus a
tlrwtic~ ti)1*111 of I~oloc~ri~lr secretio~~ illto tht. I u r n c ~ ~
of the tubulc. h u t
~IIPHC t\vt111t,~ (10 not O ( * O L I ~ s i ~ ~ i ~ ~ l t ~ i l r o ~ ~ s l y
throughout ill1 the lining
c.pithcli~~ni t i t l t l rt~g(~t~er~t.ior~ C ~ I I
o ( ~ ~ i r
from ~leighboi~rillg intact areas.
c.ot11c3s to fi)r111 i~ ring ~LIY)IIII(I 1 lit> ( I ( ~ ~ ~ I I ( ~ I ' ; L ~
i ~ ~ g
I I I I C + ~ ( ~ ~ I S .
'I'lle c*ytoplssm
tlictl~ st,;tr.lfs t,o I)rc%r~lc 111) oftc.11 fo1.1ni11g ~'~fi'illg(lllt S I ) I I C ~ U I ~ A which fall
i1ltto t811c1 IIllllc-11 of tlicb tSlll)lllr i ~ 1 1 ( 1 1l)il.Y i L ~ ~ l ' ~ ~ i L t ( '
to form concretions.
r 7
I I I ~
1.ct111it~1it o f t8hc1 u \ ~ c ~ l c ~ ~ ~ s
is itlso c.)cpc*llecl tirid tir~nlly all that remains