willard: cranial nerves of anolis carolinensis. 21 



The projection plots were made from camera drawings magnified 

 3T diameters and, except in regions of greatest complication, each 

 nerve was projected accurately throughout its entire course. In a 

 few cases some of the nerves are displaced a little from the position 

 they really occupy in the middle of their course in order to avoid too 

 great confusion of lines. Of course the essential points such as central 

 and peripheral endings and relationship of branches given off in the 

 intermediate course are strictly adhered to. 



Even after the most careful study of serial sections and reconstruc- 

 tions, one is likely to fall into error unless the work is supplemented 

 by free-hand dissections. This is particularly true in case of very 

 small branching rami or fine plexuses. Animals that are small enough 

 to be practicable for sectioning are generally too small for entire dis- 

 sections, but by the following method it was possible to make accurate 

 and fairly complete dissections of the head : — the integument of the 

 part wanted for dissection was carefully removed to avoid cutting, any 

 of the underlying muscles. Then the animal was put into the Vom 

 Rath fluid, as for sectioning, but treated a shorter time (24 to 36 

 hours). This decalcifies sufficiently well, hardens the muscles and 

 leaves them well defined because of a slight shrinkage; it also hardens 

 and blackens the nerves. Instead of further hardening in alcohol, the 

 specimen was washed out in water and put into a mixture of alcohol 

 and glycerine. It was afterwards dissected in water under a lens. 

 For best results, however, it should be dissected soon. Although the 

 whole muscle is much darkened, there is contrast enough between it 

 and the nerves to allow the identification of the finest branches of the 

 blackened nerves. The muscles are also more or less brittle, whereas 

 the nerves retain their characteristic toughness. As the dissection 

 progressed portions were removed and cleared for permanent mounts 

 in balsam. I consider the making of balsam preparations a very 

 valuable part of the technique of this work, for in no other way can 

 the fiber course in the finer anastomoses be made out. For ascertain- 

 ing the courses of nerves and for topographical relations this short 

 Vom Rath method is a valuable adjunct and the two methods — 

 sections and dissections — were constantly used together. 



For the central relations I found that properly prepared Weigert 

 preparations gave more satisfactory results than the Vom Rath, but 

 the latter method allowed the roots to be followed well into the brain 

 and in some instances served even there better than the Weigert. 

 Portions of the courses brought out by one method overlap those by the 

 other, so there could be no chance of error in combining these two 

 methods of study. 



