EXAMINATION OF CYSTICERCOID STAGES 171 



means of pins through the suckers. An incision is made in the middle 

 line along the entire length of the dorsal surface. This incision must be 

 kept purely superficial, or the intestine, which is attached to the body- 

 wall by means of a brownish tissue, will be severed. The intestinal wall 

 is whitish in colour, the dark contents showing through it. If the wall 

 is injured, the blood which the intestine contains will immediately 

 well out and the operator is warned that he has penetrated too deeply. 

 The cut edge of the body- wall is slightly lifted with the tweezers, and 

 the connective tissue between it and the intestine is severed with 

 a pair of fine scissors by means of small horizontal cuts. When 

 freed, the intestine will be found to have eleven pairs of blind sacs 

 attached to it. Of these pairs of sacs, ten are arranged diagonally 

 backwards ; while the eleventh pair, which is much longer than the 

 others, run in a backward direction upon either side of the end-gut 

 and terminate just in front of the anus. Between the saccular 

 structures, and outside the hinder pair more particularly, portions of 

 the nephridia will be seen ; and if the walls are freed well towards the 

 periphery, the two so-called lateral canals (lateral cavities) will be 

 exposed. The structural difference between the anterior and posterior 

 portions of the intestine will be apparent to the naked eye. In the 

 anterior portion the walls are thicker (ring muscles) and numerous 

 muscle-fibres, starting from the body-wall, are arranged radially 

 round the spindle-shaped pharynx. The function of the pharynx is 

 to suck blood from the wound inflicted by the jaws and to force it 

 into the alimentary tract. 1 



As soon as the intestine is freed, it should be severed behind the 

 pharynx and removed, care being taken not to injure the organs lying 

 beneath it. At the sides of the body-cavity will be seen the seventeen 

 pairs of nephridia with their terminal sacs ; in the median line is the 

 ventral nerve-cord, the anterior end of which lies hidden beneath the 

 pharynx ; between the nerve-cord and the lateral canals lie the testes, 

 nine upon either side, furnished with short, laterally directed ducts 

 attached to the vasa deferentia, which run from back to front ; in 

 front of the anterior testes lie the small ovaries and, between these, 

 the two short oviducts are seen, leading to the thicker uterus, which 

 communicates with the exterior by means of a short vagina. The 

 two vasa deferentia are continued forwards over the female genitals ; 

 their walls become thicker and they coil themselves into the so-called 



1 There is another method of preparing leeches which shows the alimentary 

 canal with great clearness. The leech is killed in chromic acid, and weak chromic 

 acid solution is introduced by means of a syringe through the pharynx into the canal. 

 The worm should be stretched, hardened, and divided into dorsal and ventral halves 

 by means of a longitudinal section. 



