4 SYDNEY EVANS JOHNSON 



are merely of historical interest. The two rays dissected by 

 Steno were probably Raia batis and the shark, which he desig- 

 nates as Canis carchariae, was identified by J, Mueller as Car- 

 charodon rondeletii, Mueller and Henle. The latter paper was 

 published in Florence in 1667, though the date usually given is 

 that of the Amsterdam edition of 1669. Since the publication, 

 in 1910, of the complete scientific works of Steno these papers 

 are readily accessible to readers. 



The illustrated memoir of Lorenzini (1678) is difficult to 

 obtain and I have not had access to it in the original. 



Savi's paper of 1844 was read, but it is relatively a side issue 

 so far as organs of the sensory canal system are concerned. He 

 figures and describes corpuscles that exist under the skin near 

 the mouth and the lips of Torpedo. On account of the obvious 

 size of the nerves of these corpuscles he regarded them as sen- 

 sory structures. 



We may take Leydig's paper of 1850 as the first step in the 

 scientific demonstration that the organs of the canal system are 

 sensory in nature. By histological studies of the knob-like 

 organs in the canals of the head of a fresh water teleost (Kaul- 

 barsch, Acerina cernua) he concludes, from their sti^ucture and 

 from their connection with a nerve, that they are sense organs. 

 He mentions those of the lateral line of the trunk but nearly 

 all that he says applies to the knob-like organs of the canals of 

 the head. He thinks at this date that the nerves cdme from 

 the trigeminus and the vagus and their fibers seem ib him to 

 terminate between the long slender cells of the sensory knobs. 



Eleven years later, F. E. Schulze ('61), then a medical student 

 working under the direction of Max Schultze at Rostock, gave 

 an analysis of the histological structure of young stages of the 

 perch (Perca fluviatilis) and of larvae of gilled amphibians 

 (Triton). His sketches show the structure of the organs not 

 only of the head region but also of the trunk. He found those 

 of the tail region similar in structure but somewhat simpler 

 than those of the head. His sketches of both perch and Triton 

 show hair-like processes extending from the sensory cells into 

 a hyaline tube and he maintains that the fibers terminate in 



