122 Sir A. E. Wright. Ow " Intertraction" between 



salt solution a coloured serum ; and in the others progressive dilutions of 

 this — the drawing effect of the salt becomes progressively less manifest, 

 becoming almost inconspicuous when we reach a 32-fold dilution of the serum. 



The concentration of the salt also influences the result. The optimum 

 display of pseudopodial interpenetration and the most rapid interfusion 

 would appear to be obtained when serum is superposed upon 5 per cent, 

 to 8 per cent, sodium chloride solutions. Very concentrated solutions give 

 less striking results, this being presumably due to the greater resistance 

 which these heavier fluids would offer to the down draught of serum. 



We have already seen in the experiment with the cottonwool plug which 

 furnished the starting point for these experiments, that solutions of egg 

 albumen react with salt in the same way as serum. This would seem to hold 

 true also of albuminous substances obtained from muscle. 



Solutions of commercial peptone give only an indistinct reaction. 



All the commoner salts — such as sodium sulphate, potassium chloride, 

 potassium sulphate, and magnesium sulphate — react with serum in apparently 

 the same manner as sodium chloride. The same holds true of solutions of 

 cane sugar, and here again very concentrated solutions give less striking 

 results. 



As in the case of diffusion proper, so here temperature exerts a dominating 

 influence. In an experiment conducted by superimposing coloured serum 

 upon 6 per cent, salt solution in diffusion cells made out of pairs of micro- 

 scopic slides, the time occupied in the descent of the serum to the floor 

 of the cell (a distance of about 2^ inches) was found at a temperature of 

 45° C. to be forty-two seconds ; at 15° C, one minute fifteen seconds ; and at 

 3° C, three minutes. 



Before embarking upon any general comment, the data of certain other 

 experiments which have a bearing upon the employment of hypertonic salt 

 solutions in the treatment of foul septic wounds may be briefly put on 

 record. The experiments are as follows : — 



Experiment 1. — Two similar capillary pipettes — A and — are taken. The 

 stems are marked off into divisions of equal length. By the aid of a teat, 

 6 per cent, salt solution is then aspirated into each — the inflow being 

 arrested when fluid comes level with the fiducial mark in the neck of the 

 stem. The ends of the capillary stems having been sealed, there is now, in 

 pipette A, imposed upon the salt solution a measured volume of a broth 

 culture of staphylococcus mixed with an equal volume of coloured water. 

 In pipette B there is imposed upon the salt solution the same quantity of 

 staphylococcus mixed with an equal volume of coloured serum. 



The tubes are now set aside for ten minutes. We then take them in hand, 



