CIRCULATION. 



497 



of the pulmonary vessels. 1 A fall in the blood- pressure in the pulmonary 

 artery, for example, produced by stimulating any nerve cannot be taken as 

 final evidence that the stimulation caused the constriction of the pulmonary 

 vessels. The lesser circulation is so connected that changes in the calibre of 

 the vessels of a distant part, the liver for example, may alter the quantity of 

 blood in the lungs. 2 The method of Cavazzani 3 avoids these difficulties. 

 Cavazzani establishes an artificial circulation through one lobe of a lung in 

 a living animal, and measures the outflow per unit of time. An increase in 

 the outflow means a dilatation of the vessels, diminution means constriction. 

 He finds that the outflow diminishes in the rabbit when the vagus is stimulated 

 in the neck, and increases when the cervical sympathetic is stimulated. Franck 

 measures the pressure simultaneously in the pulmonary artery and left auricle, 

 a method apparently also trustworthy. The stimulation of the inner surface 

 of the aorta causes a rise of pressure in the pulmonary artery and a simul- 

 taneous fall in the left auricle, indicating, according to Franck, 4 the vaso-con- 

 strictor power of the sympathetic nerve over the pulmonary vessels. A reflex 

 constriction is also produced by the stimulation of the central end of a branch 



FIG. 130. The excitation of the central end of the inguinal branch of the crural (sciatic) nerve causes 

 a rise in the aortic pressure (Pr.A.F.), a rise in the pressure in the pulmonary artery (Pr.A.P.) of 10 to 16 

 mm. Hg, accompanied by a falling pressure in the left auricle (Pr.O.O.) (Franck, 1896, p. 184). The rise 

 of pressure in the pulmonary artery, together with the fall in the left auricle, demonstrate, according 

 to Franck, a constriction of the pulmonary vessels. 



of the sciatic, intercostal, abdominal pneumogastric, and abdominal sympa- 

 thetic nerves 5 (see Fig. 130). 



Heart Vaso-motor fibres for the coronary arteries of the heart have been 

 described in the vagus of the dog 6 and cat. 7 



1 Literature : Openchowski, 1882, p. 233 ; Franck, 1889, p. 555 ; Bradford and Dean, 1889, 

 i.-iv.; 1889, p. 369; Couvreur, 1889, p. 731 ; Franck, 1890, p. 550;' Arthaud and Butte, 1890, 

 p. 12; Knoll, 1890, p. 13; Cavazzani, 1891, p. 32; Doyon, 1893, p. 101 ; Henriques, 1893, p. 

 229 ; Bradford and Dean, 1894, p. 34 ; Franck, 1895, pp. 744, 816 j 1896, p. 178. 



2 Tigerstedt, 1893, p. 493. 3 Cavazzani, 1891, p. 35. 

 4 Franck, 1896, p. 178. 5 Franck, 1896, p. 184. 



6 Martin, 1891, p. 291. ? Porter, 1896, p. 39. 



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