172  Elementary  Dispensing  Practice.       { AmAprlii.'£o4arm' 
Under  prescription  reading  Mr.  Ince  says:  «  When  a  physician 
writes  a  prescription  tor  a  patient  in  the  well-known  semi-classical 
manner,  the  dispenser  must  be  able  to  understand  what  has  been 
written  before  he  can  rightly  fulfil  the  intentions  of  the  prescriber. 
"  These"  intentions  are  expressed  in  technical  contracted  Latin, 
definite  and  perfectly  intelligible  when  once  mastered  ;  far  more 
definite  than  instructions  conveyed  in  English,  and  less  liable  to  be 
misunderstood." 
The  importance  of  being  thoroughly  familiar  with  these  various 
technical  and  usually  much-abbreviated  words  and  terms  is  well 
illustrated  by  two  letters  that  have  but  recently  appeared  in  Ameri- 
can Medicine  (Dr.  J.  M.  Miller,  Am.  Med.,  1904,  p.  380,  and  Dr.  L.  D. 
Sheets,  Am.  Med.t  1903,  p.  1014),  in  which  the  writers  complain  that 
the  Latin  term  ad  had  been  repeatedly  mistaken  for  the  English 
word  add.  Mr.  Ince  calls  attention  to  this  same  possibility,  and 
says  that  the  difference  between  ad  and  add  should  be  carefully 
noted.  uAd  is  a  preposition  which  governs  the  accusative  case  and 
means  up  to,  or  up ;  Q.  S.  quantum  sufficiat  (as  much  as  may  be  suf- 
ficient) often  precedes  ad.  Add,  when  used  in  connection  with 
Latin  abbreviations  or  directions,  is  itself  an  abbreviation  of  the 
Latin  word  adde  (add  thou)."  More  often,  however,  it  is  used  as 
the  English  word  add. 
Considerable  attention  is  given  to  the  discussion  of  the  use  and 
non-use  of  heat  in  making  simple  solutions  The  application  of 
heat  to  effect  solution  demands  considerable  knowledge  of  the  phy- 
sical properties  of  drugs  and  chemicals.  "  It  is  obvious  that  to  apply 
heat  to  substances  that  are  themselves  readily  soluble,  or  are  readily 
decomposed  or  volatilized,  would  be  considered  poor  dispensing 
and  would  betray  a  want  of  common  sense." 
In  this  connection  it  is  also  quite  necessary  to  have  considerable 
knowledge  of  the  comparative  solubility  of  substances  in  hot  and  in 
cold  water.  Potassium  chlorate,  for  instance,  being  sparingly  solu- 
ble in  cold  water  and  readily  soluble  in  boiling  water,  is  best  treated 
without  heat  to  avoid  the  large  crystals  that  are  invariably  formed 
by  this  substance  on  cooling. 
Of  powders  Mr.  Ince  says  that  they  should  be  weighed  out  one  by 
one:  "It  is  bad  practice  to  take  the  total  weight  ordered  and 
divide  it  subsequently  into  the  required  number  by  the  aid  of  a 
spatula,  not  by  the  scales  and  weight.    It  is  worse  to  dip  out  grain 
