554 S. AVALTER HANSON 



In a second series of experiments six successful transplantations 

 were made. These fall into two groups according to the period 

 of survival. In the first group of three, one rat was allowed to 

 live two days, one three, and one four days. In the second group 

 of three, one was killed on the 13th, one on the 17th, and one on 

 the 18th day. In these six experiments all the animals used were 

 half grown or young adults. 



Our observations on the first group confirm those of others 

 on transplanted ganglia. The ganglion lies imbedded in the 

 brain surrounded by a small amount of clot (fig. 2, a) . All of 

 the cells on the interior of the ganglion are dead. A few cells 

 near the periphery of the ganglion have survived. These living 

 cells stain much darker than the dead ones and sometimes show 

 a clear neurofibrillar network. They are always surrounded by 

 a wealth of new-formed fibers (fig. 2, h) . Some cells seem to have 

 undergone a temporary reaction and then succumbed (fig. 2, d). 

 Ever;y"vvhere in the neighborhood of reacting cells, branching fibers 

 and plexuses (fig. 2, e) are to be seen. In most of these reacting cells 

 it is not possible to distinguish the original axon, which has prob- 

 ably either entirely disappeared or broken up into fine branches. 

 The cell is surrounded by a plexus of branching fibers, irregular 

 in their contour, with swellings in their course, and often ending 

 in bulbs or rings (figs. 3 and 4). The fine fibers may arise either 

 directly from the cell body or from the coarse branches, and the 

 fibers often unite in a true plexus formation. These new-fonned 

 fibers closely resemble those seen in the early stage of regenera- 

 tion of a peripheral nerve. 



The grafts of 13, 17, and 18 days' standing presented a very 

 different picture, since the living cells in them had returned to a 

 condition approaching the normal. This restoration was prob- 

 ably rendered possible by several favorable factors in the tech- 

 nique. In the first place, the second cervical ganglion of the 

 rat is a very small piece of tissue, through which nutrient fluids 

 can penetrate easily. It is readily isolated and handled without 

 injury to itself by grasping the attached nerve with fine tissue 

 forceps. No sutures were needed to hold it in place in the brain, 

 and it seems probable that the brain may be a more favorable 



