76 
SULPHURETTED  HYDROGEN  ETC.  IN  TOBACCO  SMOKE. 
I  found  that  they  are  not  rejected  from  the  tables  of  the  fash- 
ionable inhabitants  of  the  capital." 
The  more  recent  observation  of  Messrs.  Saussure,  Salle',  Valet 
D'Aoust,  &c,  have  confirmed  the  facts  already  stated,  at  least 
in  the  most  essential  particulars. 
The  insects  which  principally  produce  this  animal  farina  of 
Mexico,  are  two  species  of  the  genus  Qorixa  of  Geoffroy,  he- 
mipterous  insects  of  the  family  of  water-bugs.  One  of  these 
species  has  been  described  by  M.  Guerin-Me'neville  as  new,  and 
has  been  named  by  him  Corixa  fermorata.  The  other,  identi- 
fied in  1831  by  Thomas  Say,  as  one  of  those  sold  in  the  mar- 
ket at  Mexico,  bears  the  name  of  Corixa  mercenaria. 
The  eggs  of  these  two  species  are  attached  in  innumerable 
quantities  to  the  triangular  leaves  of  the  carex  forming  the  bun- 
dles which  are  deposited  in  the  water.  They  are  of  an  oval 
form,  with  a  protuberance  at  one  end  and  a  pedicle  at  the  other 
extremity,  by  means  of  which  they  are  fixed  to  a  small  round 
disc,  which  the  mother  cements  to  the  leaf. 
Among  these  eggs,  which  are  grouped  closely  together,  and 
sometimes  fixed  one  over  another,  there  are  found  others,  which 
are  larger,  of  a  long  and  cylindrical  form,  and  which  are  fixed 
to  the  same  leaves.  These  belong  to  another  larger  insect,  a 
species  of  Notonecta,  which  M.  Guerin-Meneville  has  named 
Notonecta  imifasciata  London  Pharm.  Journ.,  Sept.,  1858, 
from  Journal  de  Pharmacie. 
ON  THE  AMOUNTS  OF  SULPHURETTED  HYDROGEN  AND 
HYDROCYANIC  ACID  IN  TOBACCO  SMOKE. 
By  A.  Vogel,  Jun.  and  C.  Reischauer. 
If  tobacco  smoke  be  passed  through  an  alcoholic  solution  of 
neutral  or  basic  acetate  of  lead,  the  incurrent  tube  soon  becomes 
blackened  in  a  remarkable  manner,  whilst  in  the  fluid  itself  a 
precipitate  of  carbonate  of  lead  rendered  brown  by  sulphuret  of 
lead  is  deposited.  To  obtain  the  sulphuret  of  lead  uncontamin- 
ated  with  carbonate  of  lead  in  the  following  quantitative  investi- 
gations, the  tobacco  smoke  was  passed  through  an  alcoholic 
solution  of  acetate  of  lead  strongly  acidified  with  acid.  The 
