260 CIRCULATION OF THE BLOOD. 



The following numerical results are derived from one of 

 Ludwig and Cyon's experiments : Previous arterial pressure, 

 90 millimetres; after division of left splanchnic, 41 mill.; 

 during excitation of peripheral end of divided nerve, 115 mill.; 

 after division of right splanchnic, 31 mill. After section of 

 both nerves, the vessels of all the abdominal viscera are seen 

 to be dilated. The portal system is filled with blood ; the 

 small vessels of the mesenter}', and those which ramify on the 

 surface of the intestine are beautifully injected, the vessels of 

 the kidneys are dilated, and the parenchyma is hyperaemic ; all 

 of which facts indicate, not merely that by the relaxation of 

 the abdominal bloodvessels a large proportion of the resist- 

 ance to the heart is annulled, but that a quantity of blood is, 

 so to speak, transferred into the portal system, and thereby as 

 completely discharged from the systemic circulation as if a 

 great internal hemorrhage had taken place. 



PART II. THE HEART. 



SECTION V. THE MOVEMENTS OF THE HEART. 



The method of demonstrating the movements of the heart, 

 stated in the order of their importance, are the following: 1. 

 Exposure of the contracting heart in situ. 2. Application of 

 instruments to the prseeordia, for the purpose of measuring the 

 cardiac movements of the wall of the chest. 3. Listening to 

 the sounds of the heart. 4. Imitating the movements of the 

 living heart by the production of similar passive movements 

 in the dead heart. 



57. Study of the Movements of the Heart in the 

 Frog. Before beginning the study of its movements, an ade- 

 quate knowledge of the form and anatomical relations of the 

 organ must be gained by dissection. For this purpose, the 

 heart and great vessels should be filled with some solid sub- 

 stance which can be rendered fluid by warming it ; such, for 

 example, as cacao butter or the ordinary gelatin mass (see 

 Chap. VI.). This must be injected by the vena cava inferior 

 in sufficient quantity to fill the heart and great vessels (see 

 fig. 228). It is then seen that the organ, as a whole, is egg- 

 shaped ; but is more or less flattened from side to side by a 

 furrow which crosses the heart nearly at right angles to its 

 axis, but inclines downwards towards the left; it is divided 

 into an upper globular (formed of the two auricles) and a 

 lower conical part (the ventricle). On its anterior aspect, the 

 ventricle is continuous with a cylindrical prominence (the 

 bulb), which projects from the anterior aspect of the right 

 auricle, and terminates above by dividing into two arteries, the 



