METHODS OF INVESTIGATION 



29 



as far as possible how far the 

 active substances are identical 

 in different tissues. The pre- 

 sent writer, working in con- 

 junction with Dr. Cramer, 

 found that there are two groups 

 of substances in watery ex- 

 tracts of nervous tissues, which, 

 when injected into the veins of 

 an animal, lower the blood- 

 pressure. Both of these groups 



FIG. 7. Dog. A.C.E., morphine, curare, arti- 

 ficial respiration. Upper curve = intestine ; 

 middle'curve limb ; lower curve = carotid 

 blood-pressure. Injection of 5 c.c. saline 

 decoction striped muscle of rabbit (Vincent 

 and Sheen) . 



FIG. 6. Dog. A.C.E., mor- 

 phine. Injection of 5 c.c. 

 " protein " extract of 

 striped muscle (Vincent 

 and Sheen). 



are soluble in water. 

 One group is easily 

 soluble in absolute 

 alcohol, and the other 

 scarcely soluble in this 

 fluid. The alcoholic 

 solution contains two 

 depressor substances ; 

 one of them has its 

 effect abolished by 

 atropin, the other has 

 not. The latter is 

 the more powerful, 

 but rather the less 

 soluble in alcohol. 

 The alcoholic solution 

 gives an abundant 

 precipitate with plati- 

 num chloride. Only a 

 small part o'f this is 

 readily soluble in 

 water, and on purify- 

 ing gives octahedra 

 and prismatic crys- 

 tals. The greater part 

 of the precipitate 



