The Hog Louse 715 



This fluid was first used by Pampel (1914:298) in his work on the female 

 Ichneumonidae, and he found that it liept the tissue soft and elastic for 

 dissecting purposes. After chloroforming, a small slit was cut in the side 

 of the abdomen to allow the preserving fluid to penetrate more rapidly. 



Owing to the toughness of the cuticula, dissections could not be made 

 on slides, and so the lice were fixed to the top of a thin layer of paraffin 

 in the bottom of a watch glass and covered with physiological salt solution. 

 Scalpels with curved blades, microscope scissors, and fine needles were 

 used, and all dissections were made under a Zeiss binocular. After some 

 practice the different systems could be removed intact and' placed on 

 slides in a drop of salt solution, where the parts could be arranged in the 

 desired way and fixed in position with Bless' fluid according to the method 

 followed by Patton and Cragg (1913:718-720). The material could then 

 be carried through the alcohols and stained in toto. The best result in 

 such staining has been obtained with Grenacher's borax carmine, the 

 stain being allowed to act for from twenty-four to forty-eight hours. 

 In dissecting organs for sectioning, the physiological salt solution was 

 replaced by the medium in which the tissue was fixed. 



In the study of the epithelium of the digestive tract, the alrmentary 

 tract was dissected out and prepared for imbedding in paraffin. In order 

 to cut more than one stomach at a time, the method learned by Minchin 

 from fellow workers in the Zoological Station at Naples in 1891, and 

 used by Minchin and Thomson (1915:508) for sectioning the stomachs 

 of fleas in their study of the rat trypanosome, was tried. Their method 

 consisted of cutting thin free-hand sections of am3doid liver, arranging 

 three stomachs on it with the anterior borders level, and fixing them in 

 position with a drop of all^umen fixative. This block could be oriented 

 easily, but it was found more satisfactory to simply imbed single alimentary 

 tracts. 



In sectioning whole lice it was necessary to douljlc-imljed in celloidin 

 and paraffin, and three methods were followed, all of which gave equally 

 good results. The slow method of celloidin imbedtling, beginning with 

 a thin solution and gradually increasing the thickness until the object 

 was sufiiciently permeated with celloidin to be hardened in chloroform 

 and carried on to paraffin in the usual way, was first tried. Then, in order 

 to shorten the period of infiltration, a modification of Gilson's rapid 

 method (Lee, 1905:131) was substituted. At the same tune the oil- 



