METHODS OF INVESTIGATION 



27 



extracted, not only from nervous tissues, but also from all kinds 



of muscular tissue, kidney, liver, spleen, testis, pancreas, ovary, 



and lung. They note, also, that other observers have extracted 



a depressor substance 



from thyroid, thymus, 



adrenal, and pituitary 



body. 



Figs. 6 and 7 show the 

 effect of injection of ex- 

 tracts of muscle. Fig. 8 

 shows the effect of brain 

 extract for the purpose 

 of comparison. 



By this time it had 

 become tolerably clear to 

 the present writer that all 

 animal tissues impart to 

 watery or saline extracts 

 a substance or substances 

 which, when injected into 

 the circulation of a living 



animal, affect the arterial 



blood-pressure. The effect 



produced by these sub- 

 stances is depressor, with 



the exception of the 



medulla of the adrenal 



[ ' ' paraganglion supra- 



renale " (Kohn)], other 



groups of chromaphil 



cells, and the infundi- 



F IG . 2. Dog. A.C.E., morphine, curare, 



artificial respiration. Hind -limb 

 plethysmograph. Hooks in auricle 

 and ventricle. Injection of 2 c.c. 

 saline decoction spinal cord (Osborne 

 and Vincent). 



bular portion of the 

 pituitary body. It had 

 also been rendered prob- 

 able that these depressor 

 effects of an extract are 

 not to be regarded as an indication of an internal secretion on 

 the part of the tissues in question. This seems now to be 

 generally recognized, and the view is adopted in the majority 

 of textbooks. 



It is naturally of some interest and importance to ascertain 



