366 On the Morphology of the Semicircular Canals. [June, 
garden. When his cage was hung under a tree by the side-walk, 
the pedestrians would stop and wonder what bird that could be 
with so strange a plumage and so novel a song. When free in 
the garden Rob would have a good time of it, occasionally find- 
ing a dainty insect. But the dear fellow was getting old. Nine 
years is rather high for Turdus migratorious, and his appetite was 
becoming a little unnatural. He found a piece of twine, and by 
persevering succeeded in swallowing it. That was the worst 
string ever Rob got on. That western investment was the death 
of him. 
20; 
ON THE MORPHOLOGY OF THE SEMICIRCULAR 
CANALS! 
BY FRANCIS DERCUM, M.D., PH.D. 
N biology we meet, at every step, new and interesting ques- 
tions. How this or that structure arose, what this or that fact 
means, are the problems which continually present themselves. 
The data are few and scattered, yet the attempt to arrange them in 
-some logical manner is at least justifiable, and though our success 
may be doubtful, we at least take a step in the right direction. 
Such an attempt let us make in regard to the semicircular 
canals. Under the idea that these structures, like all others, were 
formed for a special purpose—were designedly made to meet 
certain ends—a great variety of functions have been assigned to 
them. Viewed in the light, however, that every organ is the 
resultant of certain definite and interacting forces, the mere 
question of actual or present use becomes a secondary one. Let 
us see what the various facts I have collected seem to point out. 
Before we attempt to understand such a complex organ as the 
ear, it would be well to look over the field of zoology to see 
whether we cannot find other and simpler organs of sense, which 
may perhaps give us the right clue. Such organs I believe to be 
the so-called mucous canals or lateral lines of fishes and amphib- 
ians. These structures, I need hardly say, have been ably demon- 
strated by Leydig, F. E. Schulze and others to be sensory. They 
- consist essentially of small areas of nerve-epithelium arranged 
in linear series along the sides of the head and body, having hair- 
cells continuous with nerves and being in every Way comparable 
1 Read before the Alumni Association of the- wer iin Department of the Univer- 
sity of Pennsylvania, March 28, 1879. 
rd 
