PRESERVATION OP THE EGGS OF HELMINTHES 109 



usually emerge from their hiding place. The pieces of bowel-wall 

 should now be removed from the tubes and the liquid treated with 

 sublimate in the manner already described. The tendency of Nema- 

 todes to swell under the influence of the normal saline may be 

 counteracted by the use of a stronger (1 to 1*2 per cent.) solution. 



Lime 1 omits the normal saline and applies cold, saturated solution 

 of mercuric chloride directly to the tubes containing the faecal 

 material. The tubes are then well shaken, closed with a cork, and 

 allowed to remain in a horizontal position. Owing to their specific 

 gravity the worms soon fall to the bottom, and Liihe believes that 

 they stretch themselves better with the glass in this position. 

 Cestodes up to 15 cm. in length may be fixed by this method and 

 will be found well extended. The further treatment is identical with 

 that described above. 



CHAPTER III. 

 EXAMINATION AND PRESEBVATION OF THE EGGS OF HELMINTHES. 



Generally speaking, the presence of Helminthes in the excretory 

 organs is to be established only by direct examination of the excreta. 

 Mature parasites, or portions of them, are less frequently encountered 

 than their ova. These differ so widely in form, size, colour and con- 

 tents, that the beginner will very soon find himself able to identify a 

 large number of varieties. This branch of helminthology has such 

 a definite practical value that the student cannot too early familiarize 

 himself with the details of its technique. Good subjects for a first 

 examination are the following : The liver-fluke (Fasciola hepaticd), 

 which is readily obtainable from abattoirs, as it is frequently present 

 in the livers of sheep ; one of the large-hooked varieties of Tseniae, 

 such as Tcenia crassicollis of cats, T. serrata, T. marginata, and 

 T. coenurus of dogs, and, wherever possible, ripe proglittides of 

 T. saginata of man; one of the species of Bothriocephalides found 

 in mammals, waders, water-birds, or fish; 2 Ascaris lumbricoides from 

 swine or from the horse, which may be obtained from abattoirs ; and 

 one of the Acanthocephales from fish, frogs, or swine. 



Fig. 30 shows the position of the uterus in the liver-fluke. Its 

 folds form a rosette lying immediately behind the large ventral sucker, 

 which is placed in the median line at the base of the head-cone. 

 A portion of the body mass in this neighbourhood is cut away and 

 teazed out on a glass slide. In the process, a large number of eggs 



1 Liihe, Centralb. f. BaU., Paras, und Inf., xxx, pt. 1, 1901, p. 167 (note). 



2 For hosts which are readily obtainable, see Linstow's " Compendium." 



