GLAND-CELLS OF INTERNAL SECRETION IN THE SPINAL 
CORD OF THE SKATES. 
By Caru Caskey SPEIDEL. 
INTRODUCTION. 
Ever since the discovery of the electrical apparatus of the skate by 
Stark in 1844, it has been the subject of investigation by many work- 
ers. Among these may be mentioned particularly Leydig, Remak, 
Keker, K6llicker, Schultze, Babuchin, Sanderson and Gotch, Ewart, 
and Ballowitz. Most of these investigators dealt chiefly with the 
histology of the electric organs and the manner in which the nerves 
terminate upon the electric disks. Babuchin discovered that the elec- 
tric organs were derived from embryonic muscle-tissue. 
Sanderson and Gotch made an experimental study of the physiology 
of the electric organs. They exposed and stimulated various parts 
of the brain and also of the body-surface of the skate, and drew the 
conclusion that an electrical center existed in the optic lobes. No 
morphological work was done. 
The first one to describe the position of the electric motor cells was 
J. C. Ewart, who had previously described the histogenesis of the elec- 
tric tissue. Reasoning that the electric motor cells should be placed 
near to the electroplaxes which they innervate, he correctly located 
these structures in the lower part of the spinal cord. He figured these 
cells as resembling in form the ordinary type of muscle motor nerve- 
cells. The chief difference was in size, the electric motor cells being 
much larger than the muscle motor cells. He found that these electric 
motor cells were present in the spinal cord only in the region opposite 
to the electric organs. He made no mention, however, of certain large, 
peculiar cells which appear in this region. 
A. Romano studied the motor electric centers of the selachian fishes, 
but evidently did not see or accurately describe these cells of the skates. 
They were first noticed and described by U. Dahlgren, and the ques- 
tion at once arose as to their function. Dahlgren suggested that these 
cells might be the real electric motor cells, and it was with this as a 
working hypothesis that this work was begun. 
The skates used in this study were collected for the most part along 
the coasts of New Jersey, Massachusetts, and Maine. The experi- 
mental work was done chiefly with the species Rava ocellata, the com- 
mon spotted skate. However, Raia levis, Raia erinacea, and Raia 
radiata were also studied. Besides these, valuable embryological 
material was turned over to the writer by Professor Dahlgren, who had 
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