44 PITCH INDUSTRIES AND CANCER 



shaken up, filtered, and neutralised. In the case 

 of the pitches, each form was finely powdered, and 

 then 10 grams of it was mixed with 100 c.c. of 

 the 5-per-cent solution of HC1, filtered and 

 neutralised. Certain quantities of the filtrates 

 were added to " coefficient jelly," which also con- 

 tained 1 c.c. of a 5-per-cent solution of sodium 

 bicarbonate ; the total was boiled and allowed to 

 set as films on microscope slides. A drop of fresh 

 citrated blood from the finger was then mounted 

 on to each film, which was incubated for ten 

 minutes at 37 C., when the lymphocytes were 

 examined. Briefly, the result may be tabulated 

 thus : 



Hence it appears :that gasworks tar contains a 

 powerful excitor of cell-division, and also an 

 augmenting substance (kinetic). The same can 

 be said of gasworks-tar pitch. Blast-furnace tar, 

 and pitch made therewith, however, while con- 

 taining a weak substance which will induce 

 divisions if its action is increased by atropine, 



1 These numbers refer to the quantities of the filtrates to be 

 added to the jelly. 



