EDITORIAL. — PEREIRA'S  MATERIA  MEDICA. 
177 
In  this,  as  in  numerous  instances  throughout  that  part  of  the  work  revised 
by  the  author,  he  has  brought  the  microscope  to  bear  in  elucidating  the 
characters  of  drugs,  especially  their  structure,  which  is  often  beautifully  il- 
lustrated with  wood  cuts.  Ten  other  species  of  Chondrus  are  enumerated 
besides  C.  crispus. 
"  Chondrus  mamillosus  is  found  in  commercial  carrageen.  Some  sam- 
ples I  found  to  be  principally  composed  Fig.  158. 
of  this  species.  The  frond  of  this  plant  is 
more  or  less  channelled ;  but  the  species 
is  best  distinguished  by  the  fructification  ;  in 
C.  crispus  the  subhemispherical  capsules 
are  imbedded  in  the  disk  of  the  frond,  pro- 
ducing a  depression  on  the  opposite  side  ;  in 
C.  mamillosus  the  spherical  capsules  are 
scattered  over  the  disk  of  the  frond,  and  are 
supported  on  little  short  stalks. (see  fig.  158.)" 
Br.  Pereira  regards  the  gelatinous  matter 
of  carrageen  as  peculiar,  although  it  corres- 
ponds in  composition  with  starch  and  bas- 
sorin,   and  like  those  substances  it  is  converted 
sugar  by  digestion  with  dilute  sulphuric  acid. 
The  article  on  Cetraria  has  been  much  extended,  especially  as  regards 
the  chemistry  and  structure  of  the  moss. 
The  subject  of  tinctorial  lichens  has  been  completely  rewritten.  The  com- 
mercial varieties  of  orchilla  weeds  and  mosses  are  referred  to  their  proper 
botanical  sources.  Litmus,  orchilla  liquor,  and  cudbear  are  treated  in  de- 
tail, especially  the  former,  upon  the  manufacture  of  which  much  light  has 
been  thrown  since  the  former  edition  of  the  work.  The  remarks  upon 
litmus  paper  are  particularly  good. 
Fermentum  CERVisiiE.  Yeast.  This  interesting  subject  has  been  extended 
from  one  page,  as  an  appendage  to  the  subjeet  Hordeum,  to  seven  pages  as 
a  distinct  article  ;  illustrated  by  eight  wood  cuts.  We  extract  the  following  : 
into  soluble  gum  and 
"Botany.  The  substance  called 
yeast  is  a  mass  of  microsco- 
pic cryptogams.  The  organiza- 
tion and  vitality  of  yeast  are 
demonstrated  by  the  form  and 
structure  of  its  particles  as  de- 
termined by  the  microscope  ;  by 
their  chemical  composition;  by 
their  reproductive  power  as  proved 
by  the  generation  of  yeast  during 
the  fermentation  of  beer ;  and 
lastly  by  the  effects  of  mecha- 
nical injuries  of  heat  and  cold, 
and  of  chemical  and  other  poi- 
sons." 
"When  submitted  to  micro- 
scopic examination,  yeast  is 
found  to  consist  of  globose,  more 
or  less  ovoidal,   ellipsoidal,  or 
Fig.  176. 
&.  microscopic  appearance  of  fresh  yeast. 
b-  represents  the  gradual  change  in  the 
character  of  yeast  cells. 
11 
