[1] Longcope and McClintock, however, conclude that permanent constriction of the superior mesenteric artery and celiac axis, as well as gradual occlusion of one or both of these vessels, may be present in dogs for at least five months without giving rise to definite and constant elevation of blood pressure or to hypertrophy of the heart. Further, they have been unable to find at autopsy on man a definite association between sclerosis of the abdominal aorta and great splanchnic vessels and cardiac hypertrophy. [Illustration: Fig. 11.--Enormous hypertrophy of left ventricle probably due to prolonged increased peripheral resistance. Note that the whole anterior surface of the heart is occupied by the left ventricle. The right ventricle does not appear to be much affected. x2/3.] In diffuse arteriosclerosis accompanied by chronic nephritis the heart is always hypertrophied. This is a result, not a cause of the condition. In the pure type, there is hypertrophy only of the left ventricle without dilatation of the chamber. The muscle fibers are increased in number and in size, and there are frequently areas of fibrous myocarditis due to necrosis caused by insufficient nutrition of parts of the muscle. In these cases the coronary arteries share in the generalized arteriosclerotic process. The openings of the arteries behind the semilunar valves may be very small. There is often thickening and puckering of the aortic valves and of the anterior leaflet of the mitral valve leading, at times, to actual insufficiency of the orifice. Later, when the heart begins to weaken, there is dilatation of the chambers and loud murmurs result, caused by the inability of the nondistensible valves to close the dilated orifices. Until the compensation is established, it is impossible to say whether or not true insufficiency is present. In senile arteriosclerosis there is the physiologic atrophy of the media to be reckoned with. This change has already been referred to. When such degeneration has taken place, the normal blood pressure may be sufficient to cause stretching of the already weakened media with or without hypertrophy of the intima. The arteries may be so lined with deposits of calcareous matter that they appear as pipe stems. More frequently there are rings of calcified material placed closely together or irregular beading, giving to the palpating finger the impression of feeling a string of very fine beads. The arteries are often tortuous, hard, and are absolutely nondistensible. At times no pulse wave can be felt.