2 Earle C. Stevenson 



of Nebraska, who at that time contemplated a study of these 

 same parasites with regard to other anatomical structures, I be- 

 gan the collection of material in and near the city of Lincoln, 

 Neb. 



Stray dogs from the smaller towns about Lincoln, and the 

 dogs taken up by the pound-master in Lincoln, were examined 

 for parasites. All but four of the thirty-five dogs examined were 

 infested with parasites of some sort. About forty specimens of 

 Taenia serrata, twenty of Taenia serialis, as well as numerous 

 roundworms and hundreds of Dipylidium caninum were found 

 in the intestines. Eight dogs carried specimens of T. serrata 

 and two contained T. serialis. 



The dogs were killed with potassium cyanide and examined 

 before becoming cold. Beginning at the stomach, the whole ali- 

 mentary tract was slit open, and the parasites when found were 

 placed in warm water and washed, then killed in corrosive 

 sublimate and preserved in 70 per cent alcohol. 



In classifying the specimens collected, each host was given a 

 serial number, and the portion of the intestine where the worm 

 was attached noted ; the parasites from each host were bottled 

 separately and the species determined later. 



In preparing the hooks for study, which was a difficult matter 

 because of their minuteness and the necessity of perfect isolation 

 from the tissue of the rostellum, the heads were cut off, then 

 placed in 35 per cent alcohol for a few minutes, and afterward 

 transferred to a drop of glycerine, which was used for a macer- 

 ating fluid because of its advantage as a mounting medium. The 

 smallness of the hooks, their fragile structure, and firm setting in 

 the tissues caused many of them to be broken in separating them 

 from the tissue ; at first about 35 to 50 per cent of the hooks were 

 either lost or broken, but with practice this loss was decreased 

 to less than 25 per cent. A pair of finely pointed needles served 

 as dissecting instruments, and a dissecting microscope gave the 

 necessary magnification for careful isolation of the structures. 

 The hooks being separated from the tissues, a cover-glass was 

 placed over the drop of glycerine containing the hooks, and 

 sealed with balsam, most of the mounts remaining intact one year 

 after preparation. 



192 



