Hardesty, spinal Ganglion Cells. 2 1 



tions occasion a double counting of the fibers contained in them. In 

 each case the strip of card-board with the specimen arranged upon it 

 was placed into a vial containing i % osmic acid and bearing a label 

 stating the date, the weight and sex of the animal, the number of the 

 spinal nerve, and whether taken from the right or leftside. After be- 

 ing subjected to the action of the fixing agent for 15 or 20 minutes, 

 the parts become stiffened sufficiently to maintain their arranged rela- 

 tions and may be gently lifted from the card-board that the fluid may 

 penetrate more freely from all sides. The larger nerves were always 

 removed into the fluid. After 12 to 24 hours in osmic acid, the speci- 

 men was washed about 12 hours in water frequently changed, and 

 then transferred to 70% alcohol. While washing, an outline sketch 

 of the specimen was made for the purpose of orientation. 



Each specimen was embedded in paraffin separately in a small pa- 

 per box on the side of which was copied the label on the vial in which it 

 was fixed, washed, dehydrated, etc. Transverse sections of the two 

 nerve roots of the trunk and dorsal branches were made of about 4 u 

 in thickness, and those from the required localities were mounted 

 serially. The sections of the nerve roots were taken from about mid- 

 way their length, while those from the trunk and dorsal branches were 

 taken close up to the peripheral side of the spinal ganglion, yet far 

 enough away to avoid any portion of the ganglion itself being in- 

 volved. Separate slides were devoted to each of the localities requir- 

 ed, and the locality mentioned in their labelling. On approaching 

 the ganglion, from whichever side the sectioning was begun, the thick- 

 ness of the sections was changed. x\ll sections involving the ganglion 

 were made 9 // thick and special attention was given to mounting 

 them serially. 



For counting the nerve fibers the photographic method, devised 

 in the neurological laboratory of the University of Chicago ('99) was 

 employed for every section except an occasional very small twig of the 

 dorsal branches. The mounted sections from a given locality were 

 first carefully looked over with the compound microscope, and one 

 suitable for photographing was picked out, that is, a perfect section 

 and one which high power showed to be flat and evenly adhering to 

 the surface of the slide. Under low power this section was marked 

 ■ by a ring of ink on the cover glass. The photographs were made 

 with the aid of the Zeiss projection apparatus. The magnification 

 employed was from 300 to 500 diameters, varying according to the 

 size of the section None of the sections in this investigation when 

 sufficiendy magnified were too large to get on a single plate of the 



