NO. 4 NERVOUS SYSTEM OF A CENTIPEDE — LORENZO 9 



III. MATERIAL AND METHODS 

 HISTOLOGICAL PROCEDURE 



Specimens assignable to Arenophilus bipuncticeps (Wood) were 

 collected in the late spring and summer in the vicinity of Florissant 

 and Bellefontaine, Mo., when these arthropods were most abundant. 

 Most of the centipedes were found under flat rocks which had a "good 

 bite" on the ground. Some were collected under the loose bark of 

 felled trees. It was found expedient to kill and fix the collections in 

 the field, or soon after capture in the laboratory. Because of their 

 cannibalistic habits, they were placed in individual containers along 

 with some of their immediate environment when it was necessary to 

 keep them alive. Sensitive to sudden changes in temperature and 

 humidity, they are not amenable to culture. 



A variety of fixatives was used. Dietrich's (Kahle's), Carney's, 

 Sinha's (1953), Bouin's, hot alcohol, and cupric trinitrophenol were 

 employed with varying degrees of success. A mixture (1:1) of 

 aqueous and alcoholic Bouin's solutions was found to give best results 

 antecedent to silver impregnation (see Bodian, 1937). The harsher 

 fixatives (Sinha's, Carnoy's) required narcotization and were aban- 

 doned. The modification of Bouin's fixative was neither too slow nor 

 too drastic and was used routinely. 



A graded series of ethanol mixed with increasing volumes of n-butyl 

 alcohol (Stiles, 1934) was used for dehydration of tissue previous to 

 paraffin imbedding. Terpineol (oil of lilac) was employed as a clear- 

 ing agent. This did not harden the cuticular material so as to compli- 

 cate sectioning. To facilitate infiltration the tips of the poison claws 

 and the distal 10 or 12 antennal articles were excised with iridectomy 

 scissors under the dissecting microscope. 



The imbedding medium was prepared by melting together nine parts 

 of Fischer tissue mat (6o°-63° C.) and one part of bayberry wax. 

 This mixture was heated over a low flame for several hours and 

 filtered to insure better texture and cutting quality. 



Material cleared in terpineol required about five changes of fresh 

 infiltration medium. When the odor of lilac is no longer detectable, 

 infiltration is complete. Although heat hardens cuticle which has been 

 treated with the more common clearing agents (i.e., xylol, toluol, etc.), 

 terpineol-cleared tissue left in the oven for over eight hours did not 

 harden appreciably. Rapid infiltration in vacuo tended to distort and 

 collapse material and was abandoned when the advantages of terpineol 

 were discovered. 



Serial sections were cut with a Spencer rotary microtome. Dry ice 



