276 'Journal of Comparative Neurology and Psychology. 



and was then washed with a solution of mercuric chloride and 

 left covered with a pad moistened in that solution, while the 

 operator cleansed his hands. From this point on, the operator's 

 hands touched nothing but the sterile instruments laid out on a 

 sterile tray; all other things were handled by an assistant. Noth- 

 ing touched the wound but the sterile instruments and sponges; 

 the wound was too small to permit of introducing the fingers for 

 any purpose. 



Thanks to the natural resistance of the animals, as well as to 

 the care taken to preserve the vigor of the tissues by the use of 

 sharp instruments and hot sponges, the aseptic precautions were 

 efficient, and not in a single case was there any sign of infection. 

 (In one animal the collodion dressing came off after four days, but 

 this one was at once discarded.) As final evidence that sepsis has 

 nothing whatever to do with the results of these experiments, it 

 may be said that in a series of animals killed five, six, seven, eight, 

 twelve, seventeen and twenty days after the operation, the wound 

 was found in perfect condition; and a microscopical study of the 

 ganglion and nerve stump stained with toluidin-blue failed to 

 show any indications of infection. 



At the autopsy, note was made of the size of the neuroma and 

 of any regeneration that had occurred. The operated nerve was 

 then carefully dissected out together with its neuroma, ganglion, 

 and roots, straightened out on a piece of card-board, and fixed in 

 I per cent, osmic acid. The left, or normal nerves, were treated 

 in the same manner as the right; but they were not used in the 

 determination of the norm, since it was theoretically possible that 

 their condition might in some way be influenced by the injury 

 inflicted on the nerve of the opposite side. And, as a matter of 

 fact, such a crossed degeneration has been reported in the ventral 

 root fibers (Braeunig '03). For this reason it was considered 

 safer to take the control material from entirely normal animals. 



After fixation in i per cent, osmic acid, the tissue was imbedded 

 in paraffin and cut into transverse sections. The sections of the 

 roots were 3 /^ to 4 /x thick ; those of the ganglion were 12 n thick and 

 arranged in serial order. When a perfect series through the gan- 

 glion was not obtained the specimen was discarded. 



The osmic acid not only stains the myelin of the nerve fibers, 

 but also brings out the nerve cells so well that no further treatment 

 is necessary. The technique of counting nerve fibers and spinal 



