388 
THE  TROPICAL  AGRICUI/riJRIS  P. 
[Dec.  I,  1896. 
Theine  Iiixs  llie  fonuula  ('01  ,0„,  consisting  of 
carbon  ami  the  gases  niimgen,  hydrogen,  and  oxy- 
gen in  chemical  coinljinalion.  in  the  jmie  stateit  is 
a white  body  crystallising  in  ncetlle-shajieil  cl■.^s- 
tals  ; it  has  no  smell,  hut  possesses  a slightly 
bitter  taste  ; it  dissohes  freely  in  hot  watei'.  It 
is  classilied  by  many  chemists  among  the  vege- 
tcable  alkaloids,  and  may  be  regarded  as  a power- 
ful stimulant  to  the  ciiculatory  and  nervous  sys- 
tem ; it  is  therefore  the  slimulaling  constitu  nt 
of  tea.  Albumin  belongs  to  the  pi oteids  or  flesh- 
formers,  but  as  it  does  not  pass  into  the  infusion 
I need  not  dwell  on  its  properties  ami  uses. 
Nitrogenous  extractives  are  unimportant  from  our 
point  of  view,  and  so  are  the  colouring  matters, 
cellulose  and  a'-^h.  The  volatile  oil  present,  how- 
ever, deserves  a few  words.  It  is  believed  to  be 
produced  in  tea  duiing  the  iiroce.ss  of  jnepaia- 
tion,  as  it  has  not  yet  been  found  in  the  fresh 
green  leaves.  ^Vhen  obtained  pure  by  distillation 
it  is  of  a yellowish  colour,  and  smells  strongly 
of  tea.  It  is  very  volatile,  and  is  the  constituent 
which  gives  to  tea  its  charactrristic  aroma,  ft 
acts  as  a narcotic  on  the  nervous  system.  Tannin 
is  the  astringent  constituent  of  tea,  tuid  is 
closely  allied  to  the  tannin  of  the  oak  lank. 
It  has  a bitter  taste  and  possesses  the  pro- 
perty of  combining  with  animal  membranes.  It 
has  a consti|)ating  action  oir  the  bowels.  It 
doe.s  not  dissoUe  out  very’  rapidly  from  the  tea- 
leaves,  but  after  about  lire  minutes  the  rate  of 
solublity  increases.  T’he  injurious  etlect  of  badly' 
jirepared  infusions  of  lea  are  maiidy  due  to  the 
tannin  |uesent.  T’annin  gives  a greenish  black 
reaction  with  chloride  of  iron  and  this  reagent  may 
be  employed  to  compare  (lualitatively  two  samples 
of  tea  for  tannin  acid.  There  are  certain  other 
organic  acids  present  in  tea  which  1 am  of  opinion 
may  exercise  a bar  niful  effect  on  digestion.  We 
arc  mainly  interested  tonight,  however,  with  the 
stimulating  coMstii irent  of  tea,  viz.,  theine.  1 have 
already  iiornted  out  that  theine  is  composed  of 
carbon,  Irydi’ogen,  nitrogen,  aird  oxy’gen,  and  I 
have  here  on  a table  the  resrrit  of  the  ultimate 
analysis  of  a portioir  of  theirre.  It  is  a very  inte- 
resting anrl  wonderful  sirliject  to  consider  how’ 
these  elemerrts  are  conrbiired  to  form  a body  like 
theine.  (’arhorr  is  a black  solid,  hydrogen 
an  inllarrrinable  gas,  nitrogerr  a gas  with 
no  very  striking  prr.perties,  oxy’gen  is 
the  gas  which  suppi/r-'s  all  combustion. 
These  eleirrents,  so  dissimilar  in  ]>roperties  from 
each  other',  are  cotrrbined  itr  suitable  proportions 
to  form  this  white  ciystalliscil  stimirlant.  A few 
experinrents  with  these  ga.sts  will  Irelj)  to  bring 
borne  this  intere.stirrg  fact  to  your  minds. 
Oxygen  gas  is  an  invisible,  iirodororts,  and  taste- 
le.ss  gas.  It  will  not  buiri  of  itself,  but  causes 
other  bodies  to  bunt  with  great  rapid  tty’.  A ]>iece 
of  sulphur,  ])hos(dioi  trs,  or  even  iron  wire  will  burn 
brilliantly  in  oxygert  ; amf  I will  trow  ]iroceed  to 
demonstrate  its  jrr  (ijicrties  to  you.  [Or.  Ooodfellow 
here  performed  a tiumher  ot  striking  and  brilli- 
ant experinrents,  showitrg  the  wonderful  po’ivers 
of  oxy’geti  in  supporting  comlmstion.]  Ilydrogert 
Ls  a light  gas,  the  liglitest  suhstarree  known  in 
fact,  and  will  irot  supprort  combustion,  being  in 
this  respect  quite  unlike  oxygen.  It  Imrr.s,  how- 
ever, very  readily  with  a blue  flame,  proditcing 
water,  and  with  air  foiius  cxjdosiAc  mixtures. 
[The  lecturer  performed  a mimhcr  of  experimerrts 
with  hy'drogen,  show  ing  its  im])ortant  ]iro|)erl,ies. ] 
Nitrogen,  the  other  const  iiuent  of  theirre,  is  also 
a gas,  but  it  will  milln'r  htrrn  nor  su])]iort 
combirstion.  It  has  few  positive  ju'operlies, 
its  chief  use  in  nature  being  to  (lilute  the 
oxygon  of  the  air,  of  which  it  forms  78  per 
corrt.  [Exjierinrerits  were  here  shown  with 
nitrogen.]  'J'he.se  elements  then  are  chemically 
combined  to  form  theine,  the  active  stiinirlatin’g 
constituerrt  of  tea.  Ui  the  bodies  which  1 have 
nientiurred  as  composing  the  tea  ieaf,  theme,  tan- 
nirr,  and  the  volatrleoil  are  the  chief  found  irr  the 
infusion.  \ eiy  lew  jicojrle  know  how  to  prepare 
tea  jiroperly.  iMarry  believe  tliat  unless  the  liquor 
be  (lark  u is  ol  rnfeiior  quality,  while  otlrers 
think  the  strong  acrid  tasle  of  the  liquid  obtained 
by  allowing  tea  to  stand  for  a long  time  indicates 
high  quality.  Thise  ideas  are  w rong.  Tire  acr  id 
taste  is  due  to  tannic  acid,  a body  which  is 
injurious  to  the  system  in  excessir  e quantities, 
and  therefore  indicaies  a badly  juepared  infusion. 
The  chief  objects  in  the  making  of  tea  are— (1)  to 
obtain  the  maximiiiii  of  tlieine  w’ith  the  minimuni 
ot  tannic  acid  ; (2)  to  develop  and  bring  out  the 
aroma.  Now  the  longer  the  leaves  steeir  in  the 
water,  the  greater  the  quantity  of  tannin  dis- 
solved out.  It  follows,  therefore,  that  to  allow 
tea  t()  brew  too  long  is  a mistake,  as  the  flavour 
is  spoiled  try  the  predominant  tannin,  and  the 
infusion  acquires  injurious  iiroperties.  Eurther 
the  aro.iiatic  oil  is  lai’gely  lost  by  evaporation  by 
■*allowiDg  the  tea  to  stand  too  long.  In  order  to 
secure  the  best  results  the  follow'ing  pla  i is  recom- 
niended.  Two  earthenware  teajiots  are  required, 
and  both  should  be  heated  dry  in  front  of  the 
lire,  'i'hedry  tea  sliould  be  placed  in  one  of  the 
pots  and  allowed  to  remain  in  the  closed  warmed 
teapot  for  about  one  minute.  This  brings  oiitthe 
aroma.  Water  wiiicli  has  just  come  to  the  boil 
should  now  be  used  in  the  pi(j[)aration  of  the  bever- 
age, and  the  whole  allowed  to  stand  li-oin  three 
to  live  minutes  according  to  the  kind  of  tea.  At 
the  end  of  this  period  the  liquor  should  be  poured 
into  the  second  heated  tea-jiot,  and  is  then  ready 
for  the  table.  Heceiitly,  many  teapots  have  been  in- 
vented witli  the  olijectol  achieving  the  same  re.sult 
without  the  bother  of  pouring  into  a second  pot. 
The  principre  in  many  is  an  ai'iangemeiit  whereby 
the  tea  is  placed  in  a sepai’ate  ve.ssel  called  the 
iiifuser,’  and  boiling  water  poured  on  in  the 
usual  way.  Alter  four  or  live  minutes  by  a 
contrivance  the  infuser  is  withdrawn  to  the 
upper  part  of  the  ]>ot,  and  thus  undue  soakin<' 
is  luereiited.  Tea  preirared  according  to  this 
])lan  contains  a fair  quantity  of  theine  and  a 
minimuni  quantity  of  tanic  acid.  The  aroma  is 
also  well  brought  out.  The  leaves  should  nol  be 
used  again  for  a second  brew,  as  a second 
liijuor  would  conlaia  a large  percentage  of  the 
tannic  and  other  organic  acids  most  iiqurious  to 
the  digestive  .system.  \Miat  are  the  'ellects  of 
properly  prepaied  tea  taken  in  moderation  ? In 
the  ordinary  properly  preiiared  infusion  the  ac- 
tion of  the  volatile  oil  and  tannin  may  be  ne- 
glected, the  ])hysiological  eHects  l.eiiig  cliielly 
due  to  the  theine.  Regarded  in  this  'li-d,t 
is  a stimulant  to  the  circulatory  syste'!'ii.  It 
quickens  the  pul.se  slightly,  and  accelerates  the 
respiration,  i'lie  theine  also  acts  specilically  on 
the  nervous  system,  stimulating  thought ' and 
mental  processes.  It  als  • acts  on  the  sTin,  in- 
creasing per.spiration.  In  this  way  it  generally 
acts  as  a relreshir  g agent  to  the  w hole  sysienl, 
and  olten  acts  so  siiecilically  on  the  brain  as  to 
cure  or  jialliate  nervous  luadaciie.s.  It  cools  the 
body,  too,  by  inducing  acliviiy  of  the  sweat  glands, 
and  its  effect  is  not  lollowed  by  any  marked  reac- 
tion. Ihitif  tea  -even  properly  'pre]iiued  - be.  tak^n 
regularly  in  exce.ss,  it  acts  injuriously  on  the 
body.  It  produces  hyper-excil'ahility,'  sleepless- 
ness, trembling  ot  the  muscles,  palpitation  of 
