416 TEXT-BOOK OF PHYSIOLOGY. 



the blood a specific material which favorably influences general 

 metabolism, Schafer and Oliver injected hypodermically glycerin 

 and water extracts, and observed at once an increased activity of the 

 heart-beats and of the respiratory movements. The effects, however, 

 were only transitory. When these extracts are injected into the veins 

 directly, there follows in a short time a cessation of the auricular 

 contraction of the heart, though the ventricular contraction continues 

 with an independent rhythm. If the vagi are cut previous to the 

 injection or if the inhibition is removed by atropin, the rapidity and 

 vigor of both auricles and ventricles are increased. Whether the 

 inhibitory influence is removed or not, there is a marked increase in 

 the blood-pressure, though it is greater in the former instance. This 

 is attributed to a direct stimulation and contraction of the muscle- 

 fibers of the arterioles themselves, and not to vasomotor influences, 

 as it occurs also after division of the cord and destruction of the bulb. 

 The contraction of the arterioles is quite general, as shown by 

 plethysmographic studies of the limbs, spleen, kidney, etc. ^Applied 

 locally to the mucous membranes, adrenal extract produces contrac- 

 tion of the blood-vessels and pallor. The skeletal muscles are affected 

 by the extract very much as they aTTISy'veratrm. The duration 

 of a single contraction is very much prolonged, especially in the 

 phase of relaxation or of decreasing energy. 



It is evident from these experiments that the adrenal bodies are 

 engaged in elaborating and pouring into the blood a specific material 

 which stimulates to increasedjictiyity the_muscle-fibej^-Qj^ieheart 

 ancLajterjes, anoT!tnis~TCsistsin maintaining the normal blood-pres- 

 sure as well as the tonicity of the skeletal muscles. An alkaloidal 

 substancewajjsjiated by Abel from extracts of this gland, to which 

 the term epinephrin ftvas given. A crystallizable substance was iso- 

 lated^, firsu .by.^ Takamine and later by Aldrich, to which the 

 given. Both substances are apparently equally 

 efficacious in causing contraction of the blood-vessels and in raising 

 the blood pressure. The question as to which of these two 

 substances represents the active principle of the gland is as yet a 

 subject of discussion. 



The Spleen. The spleen is a soft bluistured organ, oval in 

 shape, from twelve to fifteen centimeters long by eight broad and 

 four thick. It is situated in the left hypochondrium between the 

 stomach and the diaphragm. In this situation it is held in position 

 by a fold of the peritoneum which passes from the upper border 

 to the diaphragm. 



Structure. A section of the spleen shows that it consists of 

 connective tissue, blood-vessels, lymph corpuscles, and lymphoid 

 tissue. The surface of the spleen is covered by a capsule composed 

 of dense fibrous tissue, from the irmef surface of winch septa or 



