PENNIS, ON CETACEAN BONKS. 
197 
but it is very probable that the different circumstances attend- 
ing the fossilization of bones from different formations may 
have the effect of giving a somewhat different appearance to 
them^ and which must be taken into account in deciding upon 
them. To show the extent to which even recent bone may 
be decomposed^ if only exposed for some time to atmospheric 
agency,, 1 have introduced^ at fig. 16 a section of the 
spinous process of the vertebra of a porpoise picked up off 
the shore at Felixstow. In outward appearance the vertebra 
was unaltered^ but the continued action of the elements has 
obliterated all internal microscopical organization in the bone. 
You may search in vain for lacunae^ canaliculi^ or Haversian 
tubes. This same destruction of microscopical structure^ 
more or less^ I have observed in bones that have been buried 
in soil for a length of time^ as grave-yard bones^ or have been 
otherwise exposed to the action of decay ; and it is not enough 
in inquiries of this sort to acquaint ourselves with the cha- 
racters of recent or perfect bone^ but we ought also to know 
the different appearances or stages of decomposed bone^ and 
for this purpose I have examined half-decayed bone^ such as 
may lie tossing about in the soil of a garden^ or have been 
buried in loose material. However decomposed bone may 
be when even the Haversian tubes are obliterated^ yet here 
and there possibly may be found a stray lacuna with pretty 
perfect canaliculi; and so distinctive appear to be the great 
classes in this respect^ that one perfect lacuna, with its 
canaliculi, is enough to decide the class of vertebrata to 
which the bone belongs. But I fancy had I brought forward 
any fossil bone as much decomposed as the recent bone is 
that I have figured at fig. 14 and attempted to prove even 
in its decomposed state that it might have been mammalian, 
no one would have believed me. And this should teach us 
what great caution is required before we reject as not mam- 
malian any fossil bone which has been more or less exposed 
to those destrojdng influences that appear to date the be- 
ginning of their operation even in primaeval times. And it 
is a matter of great wonder that, in spite of these sinister 
influences, so much of their true characters are yet retained 
in bones that have fallen under their sway for ages ; and we 
can only account for it by the presence of an antagonistic 
principle by which organic substances are changed to fossils, 
and thus decay becomes arrested when once the magic wand 
of petrifaction has touched their particles, which before were 
ready to take wing and fly away. 
To sum up : — A very patient comparison of cetacean and 
pachydermal bone, both recent and fossil, with the Eed Crag 
