PROPORTIONS OF THE TECTORIAL MEMBRANE 17 



and man, 2f turns. He did not examine the cochlea, of the ox, 

 Wiedersheim must have taken into consideration the long basal 

 end of the cochlea which does not take part in the coil. This 

 end represents the direction of the first outgrowth of the 

 cochlear pouch of the embryo. As shown by Streeter ('07) 

 for the human, this first growth of the cochlear duct is straight, 

 the coiling taking place in its further extension. In dissections 

 of decalcified cochleae of the adult hog, it was found here that 

 this basal end is of considerable length, comparable to nearly 

 one-fourth of the basal, the longest turn of the cochlea, and that' 

 it not only does not take part in the coil but that its tip curves 

 slightly in the opposite direction as well as basal-ward. Includ- 

 ing the uncoiled basal end, the pig's cochlea, were it all coiled, 

 would comprise about 4 turns. 



The cochlea of the ox is broader and slightly less flat than 

 those of the hog and man. Measurements taken inside the bony 

 labyrinths gave, as diameters of the basal turn in vertical sec- 

 tions passing through the apex and therefore including little 

 or none of the uncoiled basal end, for the ox 8.4 mm., for the hog 

 5.8 mm. and for the human 6.7 mm. And, as heights of the 

 cochleae, measurements from the apical side of the scala vestibuli 

 in the apical turn to the basal side of the scala tympani in the 

 basal turn gave for the ox 6.7 mm., for the hog 4.4 mm. and for 

 the human 4.9 mm. In other words, these measurements indi- 

 cate that the coil of the membranous labyrinth of the ox is approx- 

 imately 8 mm. broad at the base by 7 mm. in height; that of the 

 hog, 7 mm. broad by 4 mm. in height, and that of man, 7 mm. 

 broad by 5 mm. in height. The figures given are averages com- 

 puted from measurements under the compound microscope 

 of sections of 5 different cochleae of the adult hog, 4 of the ox 

 and of 2 human cochleae. The sections of the human were not 

 so satisfactory for the purpose as were the others, owing to im- 

 perfect decalcification at the time they were cut. However, 

 they were such that the indication that the human cochlea is 

 relatively more flat than those of the hog and ox may be suggested 

 as correct. The two scalae appear relatively larger in the ox 

 than in the hog and relatively larger in the human than in either. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 18, NO. 1 



