CHAP. VIII. CONCLUDING KEMARKS, SALTS. 187 



the corresponding salts of potash do not cause inflec- 

 tion, and some of them are poisonous. Two of them, 

 however, viz. the oxalate and iodide of potash, slowly 

 induced a slight and rather doubtful amount of inflec- 

 tion. This difference between the two series is inter- 

 esting, as Dr. Burdon Sanderson informs me that 

 sodium salts may be introduced in large doses into 

 the circulation of mammals without any injurious 

 effects ; whilst small doses of potassium salts cause 

 death by suddenly arresting the movements of the 

 heart. An excellent instance of the different action 

 of the two series is presented by the phosphate of 

 soda quickly causing vigorous inflection, whilst phos- 

 phate of potash is quite inefficient. The great power 

 of the former is probably due to the presence of 

 phosphorus, as in the cases of phosphate of lime and 

 of ammonia. Hence we may infer that Drosera cannot 

 obtain phosphorus from the phosphate of potash. This 

 is remarkable, as I hear from Dr. Burdon Sanderson 

 that phosphate of potash is certainly decomposed 

 within the bodies of animals. Most of the salts of 

 soda act very rapidly ; the iodide acting slowest. The 

 oxalate, nitrate, and citrate seem to have a special 

 tendency to cause the blade of the leaf to be inflected. 

 The glands of the disc, after absorbing the citrate, 

 transmit hardly any motor impulse tc the outer 

 tentacles ; and in this character the citrate of soda 

 resembles the citrate of ammonia, or a decoction of 

 grass-leaves; these three fluids all acting chiefly on 

 the blade. 



It seems opposed to the rule of the preponderant 

 influence of the base that the nitrate of lithium 

 causes moderately rapid inflection, whereas the acetate 

 causes none ; but this metal is closely allied to sodium 



