[no subject]

[BRUSH@UConnVM.UConn.Edu]

D. Squires asked about the relationship between mammalian hair and
reptilian scales. There are a copule of theories banging about. One suggests
that hair "is homologous with "certain sensory horny appendages of aphibia and
reptiles". Histolologically, the warts of toads are different from hairs, but
the PROTOTRICHs in lizards have been considered a possibility (argued mainly
by Elias & Bortner 1957 (not a type, I know my typing is bad!). The alternative
stated in numerous places by RIC Spearman (died last year, sadly) is as
follows: "in the absence of fossil material...the weight of evidence from
embryology, histology, and histochemistry supports the...theory that hairs are
entirely new horny appendages which arise not from scales, but from the
 epidermal hinge regions posterior to each scale."
      This is not unlike what has been suggested for feathers. On the other
hand, feather and hair follicles work very differently. On the positive side,
the proteins derived from hair, wool (and there is a lot of work here), etc
is much closer to the alpha-keratin of skin than is the phi-keratin of
feather.


Alan Brush, Physiology & Neurobiology, University of Connecticut, Storrs.
       Brush@uconnvm.uconn.edu   fax; 203-486-3303