170 FRANCIS M. POTTENGER 



action of stimulation of the sympathetic nerves and epinephrin. Inas- 

 much as the tonus of the blood vessels depends, with a few exceptions, 

 upon the sympathetic nerves alone, the degree of constriction and dilata- 

 tion must depend upon the nature and degree of stimulation ; so does the 

 action of epinephrin in the various vessels depend upon the dosage. Can- 

 non and Lyman (&) demonstrated that cats, as a rule, respond hy a fall in 

 blood pressure when small doses of this substance are administered. Com- 

 pensation is a law which operates throughout the organism, maintaining 

 the physiologic control. Vasodilatation in some vessels must be compen- 

 sated by vasoconstriction in others, or the organism would be seriously in- 

 jured ; and this occurs, whether the stimulus comes directly through the 

 sympathetic nerves or through epinephrin. Hoskins and McClure (a.) (&) 

 have determined that in a dog approximately one-fourth of a cubic centi- 

 meter of a 1 :1, 000,000 solution of epinephrin leaves the gland per minute; 

 but that it requires two-fifths of a cubic centimeter of 1 : 500, 000 dilution to 

 influence blood pressure ; therefore, only one-fourth enough is regularly se- 

 creted. The primary effect of this quantity is a depression, and it requires 

 about five times as much to raise pressure. Therefore, they conclude that 

 only one-twentieth of the amount of epinephrin is regularly secreted that is 

 necessary to raise blood pressure, and that such a pressor effect is pro- 

 duced by it only in times of stress. 



That there is a shifting of the blood from the splanchnic region to the 

 skeletal muscles has been shown by Hart-man. Hoskins, Gunning, and 

 Berry showed further that the skin vessels constrict while the skeletal 

 muscles dilate. These authors have shown that doses of epinephrin which 

 dilate the vessels of the skeletal muscles contract the splanchnic vessels, 

 and also the reverse. This fact furnished evidence from which we infer 

 that there is a general shifting of vasomotor control, according to the 

 degree of stimulation, whether the stimulus is primarily endocrin or 

 sympathetic. 



The work of Gruber pointed to the fact, which has since been elab- 

 orated by Hartman and his coworkers, that the action of epinephrin upon 

 the blood vessels is through the sympathetic motor cells, and not at the 

 myoneural junction, as is accepted for other sympathetically innervated 

 structures. They have shown that vasodilatation in the intestine and limbs 

 is prevented by cutting the nerves to these organs ; and have further located 

 the vasodilator mechanism for the intestine in the "collateral sympathetic 

 ganglia, probably the superior mesenteric," and for the limb in the "dorsal 

 root ganglia and sympathetic ganglia." 



Hoskins, TToskins and McClure, Swale Vincent, and Stewart and 

 Rogoff (a) (1} have expressed doubt whether epinephrin is of any use to 

 the animal in its normal state. Cannon and de la Paz, however, have offered 

 evidence that it is an important factor in integrating the body during 

 great emotion. 





