166 ADA R. HALL 
For a study of the time of regeneration ordinary haematoxylin 
and eosin give very good slides. For a further study of cell 
and fibrillar structure, different staining methods were tried. 
Picrosulphuric acid or Perenyi’s fluid for killing agent, with iron 
haematoxylin and orange G, gives good cell and fiber differen- 
tiation. The slides should be very heavily stained and then 
differentiated slowly for the best results. Another method 
which gives good fiber stain is Lewis’ pyroligneous acid method. 
Tissues are killed in von Rath mixture for eight days. They 
are then washed in methyl] alcohol, placed in 50 per cent pyro- 
ligneous acid solution for forty-eight hours, then washed in 
absolute alcohol for several days. Paraffin sections were cut 
10 vu thick. 
Several silver-nitrate methods were tried, but with little 
success. It was thought that the intravitam methylene-blue 
method would give clear fiber areas. This method was tried 
repeatedly, but the penetrability of the substance is poor where 
the central nerve cord and its sheath are concerned. Even 
when injected into the coelom and left for varying lengths of 
time, there seemed to be no reaction to it in the cord. 
For comparative study smears were also made. ‘These were 
of three kinds: 1) pure blood from the ventral vessel at the ante- 
rior end; 2) body fluid; 3) cicatrix fluid drawn from a cut which 
has been open a few seconds. To get only pure blood it was 
necessary to make a fine capillary pipette, lift the vessel on the 
forceps away from all other fluids, and press the pipette into it. 
The contraction of the vessel will force the blood up in the tube 
rhythmically. The other fluids were easily obtained. These 
smears were dried; some were stained by Wright’s method for 
blood corpuscles, and others directly with erythrosin and toluidin 
blue or Hardesty’s method no. 1. Films were also made and 
allowed to stand for half an hour in a moist place in order that 
the corpuscles might expand. These were then killed in cor- 
rosive-acetic fixing fluid and stained with eosin and methylene 
blue. 
