62 H. LISSER 



be readily traced, as seen in the graphic reconstruction fig. 34. 

 The ramus internus extends externally to the level of the thyro- 

 hj'oid membrane, and together with the a. laryngea superior per- 

 forates this, and divides into several branches, the main mass 

 however passing downward along the median surface of the thy- 

 reoid cartilage and over the lateral internal muscles of the larynx 

 to anastomose with the n. laryngeus inferior of the n. recurrens. 

 This anastomosis is perfectly demonstrated at this stage by the 

 wax model reconstruction. Some authorities state that in the 

 adult this ramus internus is not entirely sensorj'', but sends some 

 motor twigs to the m. interarytaenoideus. Others do not mention 

 this. I cannot satisfy myself absolutely on this point. The anas- 

 tomosis between the n. laryngeus inferior and superior is a large 

 one, and it is difficult to say where one nerve leaves off and the 

 other begins, and accordingly what distribution belongs to each. 



N. laryngeus inferior. The chief resultant portion of the n. 

 recurrens ascends along the medial surface of the lateral lobe of the 

 thyreoid gland, under and medial to the m. constrictor pharyngis 

 inferior, to the level of the articulatio cricothyreoidea, where it 

 divides into a lateral and posterior branch ; the former anastomos- 

 ing with the n. laryngeus superior (ramus internus) and innervat- 

 ing the mm. cricoarytaenoideus lateralis, thyreoarytaenoideus, 

 aryepiglotticus, and thyreoepiglotticus; the latter innervating 

 the cricoarytaenoideus posterior and interarytaenoideus (figs. 33 

 and 36). 



Nicolas ('94) describes a ganglion on the superior laryngeal 

 nerve after it enters through the thyrohyoid membrane at the 

 level of the arytaenoid eminences. In a couple of sections I have 

 noticed tissue somewhat suggestive of such a structure, but have 

 not investigated the matter carefully enough to add any thing 

 further. 



Embryo No. 128, 19.5 mm. Frontal sections 



The larynx shows about the same conditions found in the pre- 

 ceding 20 mm. embryo. It was selected for study, before wax 

 reconstructions were undertaken, and it was thought that a study 



