^"^'mlyX^^^^^^'}    Transpiration  of  Aqueous  Vapor,  etc,  227 
The  notes  of  this  case  were  taken  chiefly  at  the  time  of  attendance. 
Since  then,  I  have  seen  reports  of  several  other  instances  of  poisoning 
with  the  same  drug,  some  of  them  fatal.*  They  all  agree  essentially 
with  mine  in  the  character  of  the  symptoms  presented.  It  is  altoge- 
ther probable  that  my  patient  had  taken  much  more  than  forty  drops 
of  the  fluid  extract. — Boston  Med.  and  Surg.  Jour.^  Feh.^  1871. 
TRANSPIRATION  OF  AQUEOUS  VAPOR  BY  THE  LEAVES  OF 
PLANTS. 
Professor  McNab,  of  Cirencester  College,  England,  has  recently 
published  an  important  series  of  experiments  on  this  subject.  The 
plant  experimented  on  was  in  all  cases  the  common  cherry-laurel, 
(Prunm  laurocerasus,)  and  the  fluid  to  determ'ine  the  rapidity  of 
ascent,  lithium  citrate,  a  very  small  quantity  of  which  can  be  detected 
by  means  of  the  spectroscope.  Dr.  McNab  divided  the  results  under 
the  following  heads: — 1.  Quantity  of  water  in  the  leaves.  The  mean 
of  several  experiments  gave  63'4  per  cent.  2.  Quantity  of  water 
which  can  be  removed  by  calcium  chloride,  or  sulphuric  acid,  in  vacuo. 
This  was  found  to  be  from  5*08  to  6*09  per  cent.  3.  Amount  of 
transpirable  fluid  in  the  stem  and  leaves,  7*58  per  cent.  The  remain- 
der, from  56  to  57  per  cent.,  was  therefore  determined  to  be  fluid  in 
relation  to  the  cell-sap  of  the  plants.  4.  Rapidity  of  transpiration 
in  sunlight,  difl"used  light,  and  darkness.  The  results  given  are  : — 
In  sunlight,  3'03  per  cent  in  an  hour ;  in  diff'used  daylight,  0-59  per 
cent. ;  in  darkness,  0*45  per  cent.  5.  Amount  of  fluid  transpired  in 
a  saturated,  and  in  a  dry  atmosphere  in  the  sun,  and  in  difi"used  day- 
light. In  sunshine,  the  experiments  gave  25'96  per  cent,  in  an  hour, 
in  a  saturated  atmosphere  ;  20*52  per  cent,  in  a  dry  atmosphere  ;  in 
the  shade,  the  results  were  reversed,  nothing  whatever  in  a  saturated, 
1-69  per  cent,  in  a  dry  atmosphere.  These  results  strikingly  confirm 
the  earlier  experiments  of  Deherain,  that  evaporation  from  leaves  is 
due  to  light,  and  not  to  heat,  and  that  it  proceeds  equally  in  a  per- 
fectly saturated  atmosphere.  6.  Quantity  of  water  taken  up  by 
leaves  when  immersed  in  it.  The  mean  of  several  experiments  gave 
4-37  per  cent,  in  one  and  one-half  hours.  7.  Quantity  of  aqueous 
vapor  absorbed  by  leaves  in  a  secluded  atmosphere.    This  was  found 
*  American  Journal  of  Pharmacy,  Jan.,  1870.  American  Journal  of  the 
Medical  Sciences,  Jan.,  1867. 
