272 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



rate is accelerated, while the blood-pressure is increased sometimes to an 

 extraordinary extent. These facts are obtained with very small doses of the 

 extracts. Schaefer states that as little as 51 milligrams of the dried gland 

 may produce a maximal effect upon a dog weighing 10 kilograms. The 

 effects produced by such extracts arc quite temporary in character. In the 

 course of a few minutes the blood-pressure returns to normal, as also the 

 heart-beat, showing that the substance has been destroyed in some way in the 

 body, although where or how this destruction occurs is not known. Accord- 

 ing to Schaefer, the kidneys and the adrenals themselves are not responsible 

 tor this prompt elimination or destruction of the injurious substance. The 

 constriction of the blood-vessels seems to be due to a direct effect on the 

 muscles in the walls of the vessels, in part at least, since it is present after de- 

 struction of the vaso-motor centre and most or, indeed, all of the spinal cord. 

 Several observers 1 have shown satisfactorily that the material producing this 

 effect is present in perceptible quantities in the blood of the adrenal vein, so 

 that there can be but little doubt that it is a distinct internal secretion of the 

 adrenal. Dreyer has shown, moreover, that the amount of this substance in 

 the adrenal blood is increased, judging from the physiological effects of 

 its injection, by stimulation of the splanchnic nerve. Since this result was 

 obtained independently of the amount of blood-flow through the gland, 

 Dreyer makes the justifiable assumption that the adrenals possess secretory 

 nerve fibres. Abel 2 has succeeded in isolating the substance that produces 

 the effect on blood-pressure and heart-rate, and proposes for it the name 

 epinephrin. He assigns to it the formula C 17 H 15 N0 4 , and describes it as a 

 peculiar unstable basic body. Salts of epinephrin were obtained which when 

 injected into the circulation caused the typical effects produced by injection 

 of extracts of the gland. It is possible that the substance in question may 

 be continually secreted under normal conditions by the adrenal bodies and 

 play a very important part with reference to the functional activity of the 

 muscular tissues. 



Pituitary Body. — This body is usually described as consisting of two 

 parts, a large anterior lobe of distinct glandular structure, and a much smaller 

 posterior lobe, whose structure is not clearly known, although it contains 

 nerve-cells and also apparently some glandular cells. Embryologically the 

 t\v«> lobe- arc entirely distinct. The anterior lobe, which it is preferable to call 

 the hypophysis cerebri, arises from the epithelium of the mouth, while the 

 posterior lobe, or the infundibular body, develops as an outgrowth from the 

 infundibulum of the brain, and in the adult remains connected with this 

 portion of the brain by a long stalk. Howell 3 and others have shown that 

 extracts of the hypophysis when injected intravenously have little or no 

 physiological effect, while extracts of the infundibular body, on the contrary, 



1 American Journal of Physiology, 1899, vol. ii. p. 203. 

 ' Zeitsehrtft fur phystologisehe Chemie, 1899, Bd. xxviii. S. 318. 



• Journal of Experimental Medicine, 1898, vol. iii. p. 245; also Schaefer and Vincent : Journal 

 of Physiology, 1899, vol. xxv. p. 87. 



