54 H. LISSER 



cartilages of Wrisberg and Santorini are not present at this period 

 as definite separate structures, but there is a suggestion of the lat- 

 ter in the smaller model of this stage — an appendage of the ary- 

 taenoids — fig. 36, 



The Hyoid hone and styloid process need not be described in 

 detail. A very good idea of them can be obtained from a study 

 of figs. 28, 29 and 32. The drawings of the model, figs. 37, 38 

 and 39, show the general shape, and relation to contiguous struc- 

 tures, and the section drawings give some idea of the extent of 

 chondrification. 



THE MUSCLES 



At this stage the musculature is quite distinct and all the mus- 

 cles permit of clear differentiation. Fibrillation is fairly exten- 

 sive, especially in the cricothyreoideus and cricoarytaenoideus 

 posterior. The muscles have attained their adult relationship 

 and reconstructions reveal their character with considerable pre- 

 cision. Thus I cannot agree with Kanthack ('92), who says that 

 at four months the cricothyreoid and constrictor are in close con- 

 tact and cannot be separated one from the other ; that it is impos- 

 sible at two months to separate the interarytaenoideus and cri- 

 coarytaenoideus posterior. That up to the fourth month the fibres 

 have the same direction and that the muscles cannot be really 

 differentiated until the fourth month. He adds that it is impos- 

 sible to separate the thyreoarytaenoideus and cricoarj^taenoideus 

 lateralis, which holds also for the child and adult. Although 

 'impossible' is expressing it a bit strongly yet the latter part of 

 the statement is well taken, as even in the child and adult the dif- 

 ferentiation is not always clearly manifest. 



The m. cricothyreoideus. Figs. 29 and 31 picture this muscle in 

 section, and figs. 34 and 38 give the appearance in reconstruction, 

 both wax models and graphic representation. Its origin on the 

 external surface of the arcus cartilaginis cricoideae is as in the 

 adult. It inserts on the medial surface of the inferior margin of 

 the lamina cartilagins thyreoideae. It is a well developed mus- 

 cle with numerous evidences of fibrillations. However there is 

 no division into a pars recta and pars obliqua as in the adult, nor 



