18 IRVING HARDESTY 



The cochlea of the pig at term appears to be slightly smaller 

 than that of the adult hog. Averages of measurements taken 

 in the same way of cochlea of fetuses at about full term gave 4.8 

 mm. as the width of the coil at the base by 3.4 mm. in height. 

 Comparison indicates that the greater size of the adult is in large 

 part at least due to an evident increase in size attained by the 

 two scalae. Very probably the total length of the cochlea has 

 increased but very little in the adult. 



The length of the tectorial membrane, is somewhat less than 

 that of the cochlear duct which carries it. It does not extend 

 to touch the blind apical end (caecum cupulare) of the duct nor 

 does it extend quite to the end of the caecum vestibulare, the 

 basal end of the duct. And the duct is not*so long as the scalae 

 on its either side, especially the scala tympani. It appears from 

 the best that could be gathered from various sections and teased 

 cochleae that the tectorial membrane is quite strictly co-extensive 

 with the spiral organ. Its exact length not being the point in 

 mind at the time the dissections of the adult hog were being made, 

 only three membranes of the adult were teased out sufficiently 

 intact to determine their lengths. Two of these were decided 

 each to have a length of nearly 27 mm. and the outer about 26 

 mm. The teasing of these was done after fixation, which is 

 better for measuring since the membrane does not stretch so 

 readily. All three membranes were broken, but the pieces were 

 all saved and could be arranged in order on the slide. Accurate 

 measurement, of especially the apical or most curved turn of the 

 coil, is difficult. It has to be done in segments. Much straight- 

 ening and attempts to straighten the membrane usually in- 

 crease the sources of error. The average length obtained from 

 measurements of seven membranes of fetuses near full term and 

 two from young suckling pigs, recorded in previous paper of 

 the writer, was 25.5 mm. Some of those measurements were 

 obtained by the use of a string laid upon outline drawings of 

 the entire membrane, whole or in pieces, projected under known 

 magnification. Allowing for error in measuring it can only 

 be said that the tectorial membrane of the adult hog is probably 



