CIRCULATION. 205 



The lingual and the glossopharyngeal nerves are recognized by all authors as 

 dilators of the lingual vessels. The sympathetic and the hypoglossus contain 

 constrictor fibres for the tongue. It is possible that the lingual contains also 

 a small number of constrictor fibres. Most if not all these vasomotor fibres 

 arise in the sympathetic and reach the above-mentioned nerves by way of the 

 superior cervical ganglion. They degenerate in from three to five weeks after 

 the extirpation of the ganglion. 



Morat and Doyon cut the cervical sympathetic in a curarized rabbit and 

 examined the retinal arteries with the ophthalmoscope. They were found 

 dilated. The excitation of the cervical sympathetic caused constriction, the 

 excitation of the thoracic sympathetic dilatation of these vessels. The retinal 

 fibres leave the sympathetic at the superior cervical ganglion and pass along 

 the communicating ramus to the ganglion of Gasser, whence they reach the 

 eye through the ophthalmic branch of the fifth nerve, the gray root of the 

 ophthalmic ganglion, and the ciliary nerves. Most, or all, of the fibres for 

 the anterior part of the eye are found in the fifth nerve. 



Lungs. — The methods ordinarily employed for the demonstration of vaso- 

 motor nerves cannot without danger be used in the studv of the innervation 



Fig. 45.— 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.G.) (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 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. The method of Cavazzani avoid- these difficulties. 

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



1 Doyon : Archives de Physiologic, 1893, p. L0] ; Henriques : SkaTidinavisches Archiv fur Physi- 

 ologic, 189.3, iv. p. 2'2\) ; Bradford and Dean : Journal, of Physiology, L894, xvi. p. 34 ; Franck: 

 Archives de Physiologie, L896, |>. L78. 



