IV. OF RANA PIPIENS. 31 



yet its distribution and properties are widely different. The branches from the 

 common trunk resulting from the union of the nerve from the trigeminal ganglion 

 and that from the vagus are three, liable, however, to slight variety, sometimes there 

 being but two, and one of these giving off the third. 



a. The first of these (Plate II. Fig. 2, h) is directed forwards and outwards, and 

 passes over the tympanic and pterygoid bones just above the articulation of the 

 lower jaw ; it gives a small filament to the walls of the cavity of the tympanum, 

 after passing which it divides into two terminal branches, one of which is distrib- 

 uted to the skin behind the angle of the jaw, and to the sides of the throat in the 

 neighborhood of the cicatrices formed by the obliteration of the openings through 

 which the fore legs are protruded when they first appear externally ; the second is 

 directed forwards, and is lost on the skin covering the angle and the posterior half 

 of the lower jaw ; near its termination this last branch forms an anastomosis with 

 the external lower jaw branch of the trigeminus. 



b. The second trunk of the facial (Plate II. Fig. 2, i) descends along the horns 

 of the OS hyoides, but in its passage no branches were detected until it reached the 

 line of union between the mylo-hyoid muscle and the skin (which occurs on either 

 side, midway between the median line and the branch of the lower jaw) ; there it 

 passes to and is distributed in the skin covering the throat between the angles of 

 the lower jaw under the larynx and in front of the sternum. No branches what- 

 ever were traced to any of the muscles among which it passed, 



c. This is the larger of the three (Plate II. Fig. 2, k) ; it passes inside of the 

 angle of the jaw, reaches the inner surface of this last, and follows the line of union 

 between the mylo-hyoid and lower jaw as far forwards as the symphysis. In its 

 course it gives filaments to the mucous membrane of the floor of the mouth, espe- 

 cially at the posterior part, corresponding with the position of the air-sacs of the 

 male ; the largest portion of its terminal filaments reach the mucous membrane at 

 the union of this last with the jaw, and are all given off from the convex side of 

 the nerve ; all are therefore directed outwards. This branch, however, is not in 

 close company with the lower jaw branch of the fifth, as stated by Stannius, though 

 they run a parallel course. 



According to the description just given of the nerves derived from the trunk 

 formed by the union of branches from the trigeminal ganglion and the vagus, it 

 must, reasoning from analogy, be endowed mainly, if not wholly, with sensitive 

 properties. No filaments were traced to muscles, though it is not impossible that 

 some minute muscular filaments may have escaped notice; if any do exist, they 

 were too small to be seen with a lens magnifying three diameters, after the prepara- 

 tion had been immersed in dilute nitric acid. The correctness of this investigation 

 by anatomy is confirmed by the evidence derived from galvanism, for the application 

 of this agent when the nerve was fairly insulated produced no muscular contrac- 

 tions ; and we might add in evidence the negative fact, that the muscles of mastica- 

 tion and those of the hyoid apparatus are respectively supplied from the lower jaw 

 branch of the trigeminus and the hypoglossus nerves. From what has been said, 

 then, it follows that the so-called facial, even if we admit the existence of motor 



