452 



THE ORGANS 



(5) Cells of Golgi Type II 



The axones of these cells do not leave the gray matter, but 



divide rapidly and terminate in the 

 gray matter near their cells of origin, 

 some crossing to terminate in the 

 gray matter of the opposite side. 



TECHNIC 



(i) For the purpose of studying the 

 spinal ganglion cell with its processes and 

 their relations to the peripheral nerves and 

 to the cord, the most satisfactory material 

 is the embryo chick of six days' incubation, 

 treated by the rapid silver method of Golgi 

 (technic b, p. 36). Rather thick (75/i) 

 transverse and longitudinal sections are 

 made and mounted in balsam without a 

 cover-glass. Owing to the uncertainty of 

 the Golgi reaction, several attempts are 

 frequently necessary before good sections 

 are obtained. 



(2) The root cells of the anterior horn 

 with their axones passing out of the cord 

 and joining the peripheral processes of the 

 spinal ganglion cells to form the spinal 

 nerves, can usually be seen in the trans- 

 verse sections of the six-day embryo chick 

 cord prepared as above, technic (i). 



(3) For studying the column cells of 

 the cord, embryo chicks of from five to six 

 days' incubation should be treated as in 

 technic (i). Owing to the already men- 

 tioned uncertainty of the Golgi reaction, it 

 is usually necessary to make a large num- 

 ber of sections, mounting only those which 

 are satisfactorily impregnated. It is rare 

 for a single section to show all types of 

 cells. Some sections contain tautomeric 

 cells, some contain heteromeric, some both, 

 while in very few will the hecateromeric 

 type be found. 



Sections containing fewest impregnated 

 cells frequently show collaterals to best 

 fringe of fine transverse fibres crossing the 

 and white matter. 



Fig. 318. — From Longitudinal 

 Section of Spinal Cord of Embryo 

 Chick. (Cajal.) A, White column 

 of cord; B, gray matter. The cells 

 of the gray matter (column cells) are 

 seen sending their axones into the 

 white matter, where they bifurcate, 

 their ascending and descending arms 

 becoming fibres of the white column. 

 The dendrites of these cells are seen 

 ramifying in the gray matter. To 

 the left are seen fibres (posterior root 

 fibres) entering the white matter and 

 bifurcating, the ascending and de- 

 scending arms becoming fibres of the 

 white column. From the laiter are 

 seen fibres (collaterals and terminals) 

 passing into the gray matter and end- 

 ing in arborizations (Golgi Method). 



advantage. These are seen as a 

 boundary line between gray matter 



