Am.  Jour.  Pharm  ) 
January,  1921.  j 
Spiders  Used  in  Medicine. 
19 
(to  which  the  spiders,  but  not  the  insects,  belong)  contains  sev- 
eral orders,  such  as  the  scorpions,  that  are  closer  akin  to  the  spiders 
than  are  the  insects.  Most  of  these  are  so  distinct  in  superficial 
appearance  that  there  is  little  probability  of  their  being  mistaken 
for  spiders. 
If  one  will  remember  that  spiders  have  four  pairs  of  legs, 
apparently  no  antennae,  and  that  their  head  is  not  separated  from 
the  thorax  by  a  neck-like  constriction,  there  need  be  no  trouble 
to  distinguish  them  from  insects ;  which  have  three  pairs  of.  articu- 
lated legs,  one  pair  of  antennae,  and  head  and  thorax  separated  by 
a  distinct  "neck."  In  the  class  Arachnida,  spiders  may  be  easily, 
separated  from  other  orders  by  remembering  that  thorax  and  abdo- 
men are  separated  by  a  short,  slender  stalk,  and  the  abdomen  is  not 
segmented.  In  their  nearest  relatives,  the  mites,  the  thorax  and 
abdomen  are  fused  and  sack-like. 
(A)  Diagram  of  a  Spider.  The  head  and  thorax  are  fused,  the 
abdomen  is  not  segmented;  there  are  four  pairs  of  legs;  there  are 
no  antennae,  but  a  pair  of  leg-like  pedipalps  arises  in  front  of  the 
first  pair  of  true  legs. 
(B)  Diagram  of  an  Insect.  The  head  and  thorax  are  sepa- 
rated by  a  "neck";  the  abdomen  is  segmented;  there  are  but  three 
pairs  of  legs;  a  pair  of  true  antennae  arises  from  the  head  in  the 
region  of  the  eyes. 
Since  very  early  times  many  people  have  looked  upon  spiders 
with  unfounded  dread  and  superstition.     During  the  medieval 
