The American journal of the medical sciences . e a micro-scopic examination of the chiasma of thelaryngeal nerve in the iguana (Fig. VI.)? ^^^find their inferences fully confirmed; thestructure of it being, in its essential features,like that of the hypoglossal nerve in theostrich. It presented the following irregularity: The fibres from the trunk,a, are divided into two strands, one of which passes forwards on the sameside, and the other, h, crosses in a single mass to the opposite side. Thosefrom the trunk, a, divide into three parcels ; one going forwards is separa-ted from the decussating
The American journal of the medical sciences . e a micro-scopic examination of the chiasma of thelaryngeal nerve in the iguana (Fig. VI.)? ^^^find their inferences fully confirmed; thestructure of it being, in its essential features,like that of the hypoglossal nerve in theostrich. It presented the following irregularity: The fibres from the trunk,a, are divided into two strands, one of which passes forwards on the sameside, and the other, h, crosses in a single mass to the opposite side. Thosefrom the trunk, a, divide into three parcels ; one going forwards is separa-ted from the decussating fibres of a by an interval filled with fatty matter;a second, c, crosses to the opposite side in a manner nearly symmetrical withh ; and the third, d, the smallest, crosses still further forwards. These twocomprise all the decussating fibres from a toward a. As the bundles h andc pass each other, their fibres become separated and spread out after the Larynx of Alligator.—a, constric-tor ; ?;, dilator; 1, laryngeal nerve andchiasma. Fig. Chiasma of the laryngeal nerve ofthe Iguana. Researches, p. 35. 1864.] Wyman, Passage of Nerves across Middle Line of Body. 349 manner of nerve fibres in a ganglion. The fibres of d pass over thechiasma free. This arrangement gives an unsymmetrical character to theparts, but is most probably only an individual peculiarity. It appears from what has just been stated that various peripheral nervesfrom opposite sides of the body form decussations with each other, all ofwhich can be traced by dissection without the aid of the microscope, or atmost requiring that of a very low power. The nerves which contribute tosuch interchanges of filaments are the fifth, the hypoglossus, the laryngeal,and post-tracheal branches of the vagus, the phrenics, and the Mitchell and Morehouse have demonstrated what had not been pre-viously observed, that in turtles the upper laryngeal nerves form a symme-trical chiasma, to which the right and left
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