Tlie Motor Ganglion Cells of the Frog's Spinal Cord. 51 



ON THE MOTOR GANGLION CELLS OF THE FROG'S 

 SPINAL CORD. 



By E. A. BiRGE, Ph. D., Professor of Zoology, University of Wisconsin. 



The following paper was originally published in the 

 ^•' Archiv fiir Anatomie and Physiologie;' for 1883. A syn- 

 opsis of the work is here presented in English. 



The reason of our defective knowledge of even the most 

 important numerical relations of the elementary structure 

 of the body lies in the incomplete methods of investigation 

 which were formerly employed. Stilling's attempts to 

 determine the number of the elements of the central nerves 

 system have not been carried further, because the means of 

 investigation were too imperfect to secure certain results 

 even with the greatest care and industry. Rough approxi- 

 mations only were made, which naturally were often in- 

 correct. The enumerations recently made of the fibers of 

 the optic, and of certain spinal nerves have shown that the 

 more perfect methods now at our command, have brought 

 us nearer to accurate results. 



The method of saturating the specimens with a sub- 

 stance which binds all parts together and gives them a like 

 consistency, obviates one of the greatest dangers to be found 

 in counting the cells of an organ, viz., the loss or destruction 

 of part of the cells. Further in the possibility of staining 

 specimens en masse, in perfect and rapid microtomes, in the 

 accurate arrangement of specimens upon the slide, we have 

 gained means which reduce to the work of a few months, 

 tasks, for which, a decade since, a life-time would not have 

 sufficed. 



Two conditions must be fulfilled in the counting of the 

 cells of an organ. The cells must be brought under the mi- 

 croscope without loss, and must be so colored that they can 

 be at once and easily distinguished. If these conditions are 

 met, the enumeration will be easy and quick, as well as trust- 

 worthy; but if one must deliberate whether to count certain 



