646 RAYMOND PEARL. 



The following substances were used in the experiments 



/-Nitric 

 Mineral acids . \ Hydrochloric 



ISu 



Iphuric 

 Oxalic 



Organic acids . ^ Citric 



Alkalies 



Salts of heavy metals 



Other salts . 



Cane-sugar. 



I Formic 

 fSodium hydrate 

 (Sodium carbonate 

 fCopper sulphate 

 (Zinc sulphate 

 Sodium chloride 

 Sodium bromide 

 Potassium chloride 

 Masfuesium chloride 



Distilled water. 



Since distilled water was found to have a decided effect in 

 producing a reaction^ the solutions were prepared iu both 

 distilled water and in filtered tap water. In case of any 

 doubt; as with very dilute solutions, the effects of the solu- 

 tions prepared in each sort of water were tested and 

 compared. 



Since only qualitative results were desired, and for the 

 practical reason of greater convenience; perceutage rather 

 than molecular solutions were used. 



/3. Results. — The results are, in a way, so remarkable that 

 they will be presented in some detail. 



Mineral Acids. 



Nitric (sp. gr. 1*42), i per cent. — This solution causes 

 strong negative reaction. If applied to the head region the 

 animal turns away from the side stimulated immediately; and 

 strongly. If the stimulus is long continued the animal 

 writhes and twists about violently. 



Stimulation of the posterior region causes the part where 



