The lateral line system in extinct amphibia

The study of the system of canals and sense organs in the lower vertebrates, known as the lateral line system, has interested many anatomists.The existence of the lateral line system was first observed, of course, in the fishes where it is clearly marked, more especially on the body of the fish.According to Collinge ( I ) , the lateral line organs were first observed on a species of skate by Stenonis in 1664, and in 1669 on some of the sharks.The term canal was first applied to this set of structures under the preconceived idea that there was an actual canal under the skin, as indeed there seems to be in some cases, and M'Donnell ( 2 ) tells us of his attempts to inject the system of canals with a syringe.Various means were devised for studying the anatomy of this peculiar set of structures and many theories were propounded as to its possible functions.The general opinion was that the lateral line structures were secreting organs and the grooves on the crania of fishes and on the skulls of the ancient Amphibia are almost universally spoken of as sliine canals or mucous cannls or grooves.Through the recent embryological and anatomical studies of Allis, Pollard, Platt, Collinge, Cole, Parker, Takahashi, Harrison, and others, the full development and functions of the lateral line system have been made out in a few forms.It is now generally admitted, especially since the excellent experiments of Parker ( 3 ) on the function of these organs in fishes.that the lateral line system is a set of sense organs intermediate in function between the organs of touch and those of hearing, but more delicate than either in some respects.