THE ELASTICITY OF ARTERIES. 75 



Worm Mliller 1 transfused fluid to the extent of 127 percent, of the 

 body-weight. 



Similarly, bleeding to the extent of T88 to 2*82 per cent, of the 

 body-weight causes only an insignificant fall of arterial tension. The 

 velocity of the escape of the blood has a considerable influence on tha 

 change of arterial tension produced by bleeding. Sudden ansemia of 

 the bulbar centres excites, while slowly advancing ansemia, without any 

 preliminary stage of excitation, paralyses these centres. Thus it is 

 easier to obtain a fall of tension by slowly tapping a vein, than it is by 

 allowing the same quantity of blood to escape rapidly from an artery. 

 After rapid haemorrhage the heart is accelerated, the action of the respira- 

 tory pump increased, and the arterioles constricted. The blood is taken 

 from the veins, and piled up in the arteries. It has been observed in 

 the frog that the vessels contract and the tissue lymph passes into the 

 circulation after the loss of blood. 2 At the same time the secretions 

 become diminished. 



Transfusion of blood or of saline solution, in the normal animal, at 

 first raises the arterial pressure to about 170 to 180 mm., but the 

 pressure never passes much beyond this limit. If the cervical cord be 

 divided, and the arterial pressure thus lowered previous to the trans- 

 fusion, the pressure may reach to the same limit, and not beyond. The 

 reason for this is not far to seek. So soon as the arterial tension reaches 

 a certain height, the systolic output of the heart becomes less complete, 

 the residual blood in the left ventricle increases, and the diastolic 

 pressure rises. The diastolic rise of pressure in the left ventricle tells 

 back in turn on the left auricle, the pulmonary circulation, the right heart, 

 and the venous circulation. The transfused fluid thus congests in the 

 capacious reservoirs of the veins and capillaries, especially in the lungs, 

 the liver, and the abdominal organs. According to Cohnheim, 3 injections 

 of saline equal to 25 to 30 per cent, of the body- weight, or four times that 

 of the amount of the blood, does not notably increase for any length of 

 time the pressure in the femoral vein. Still larger injections may raise 

 the venous pressure to 18 or 20 mm. Hg. " These experiments show that 

 the vascular system is vastly more capacious than the accommodation 

 of the normal blood quantum demands." On microscopical examination 

 of the circulation, some of the capillaries are always seen to be empty 

 and collapsed, except in times of vaso-dilatation. Likewise the large 

 veins appear on examination normally more or less flattened, not round 

 and distended with blood. By the filling out of these vessels, the 

 capacity of the vascular system is enormously increased. On transfusion 

 of large quantities of saline, the liver becomes swollen, hard, and tense ; the 

 lungs and other tissues oedematous. Fluid is transuded, and the abdominal 

 organs become without exception markedly dropsical. Large quantities 

 of urine collect in the bladder, and the stomach and intestines become 

 distended with fluid. Almost every one of the secretions is increased, 

 and the lymph flow from the thoracic duct may become twenty-five 

 times greater than at the commencement of the experiment. In fact, 

 the leakage of fluid finally becomes as fast as the rate of transfusion, and 



1 Ber. d. Tc.. sacks. Gesellsch. d. Wissenscli. math.-phys. CL, 1873, Leipzig, S. 

 573-664. Cf. Magendie, Compt. rend. Acad. d. sc., Paris, 1838, tome i. p. 55. 



2 Klemensiewicz, Sitzungsb. d. Jc. ATcad. d. Wisscnsch., Wien, 1887, Bd. 96, Abth. 

 iii. S. 57. 



3 "Lectures on Pathology," New Kyd, Soc. Translation, vol. i. p. 457. 



