EXAMINATION OF CYSTICERCOID STAGES 



161 



The macroscopic inspection of the living parasite should be 

 supplemented by the preparation and examination of transverse 

 sections. These should be cut from well-hardened Ascarides, either 

 by hand or, after embedding in paraffin or celloidin, with the micro- 

 tome. It is best to examine, first, a section taken through the 

 anterior portion of the body, in front of the sexual organs and behind 

 the oesophagus. Within the smooth cuticle is the subcuticular layer, 

 containing cell-nuclei and fibres ; it is heaped up into four 

 thickenings, placed in the median and lateral lines. Between these 

 thickenings, and divided by 

 them into four fields, lies 

 the muscular structure, 

 composed of cells arranged 

 longitudinally ; these are 

 severed transversely in the 

 section. The muscle-cells 

 are comparatively long. 

 Each consists of a peri- 

 pheral groove-like portion 

 containing the muscle- 

 fibrillae, and of a proto- 

 plasmic portion contin- 

 uous with the groove, 

 which projects consider- 

 ably into the body-cavity 

 and contains the large 

 nucleus. With this proto- 

 plasmic portion of the 

 muscle-cells, the nerves 

 are associated ; they are 

 seen in the section stream- 

 ing out to right and left 

 from the median cords. 

 Longitudinal nerve-cords, 

 of a slighter build than the median nerves, are placed at the sides, and 

 close to them the lumens of the excretory canals will be seen. These 

 canals unite at the level of the excretory pore, close behind the 

 mouth papillae, to form a single channel. In the centre of the section 

 and distinguished by the columnar structure of its epithelium, is the 

 intestine. 



A second section should be taken from the anterior portion of the 



body at the level of the oesophagus. The oesophagus is seen to be 



a thick-walled tube with triangular lumen, which is lined with a 



continuation of the cuticle ; the walls consist of muscle-fibres arranged 



11 



FIG. 82. Diagrammatic representation of a trans- 

 verse section through Ascaris lumbricoides. In the 

 centre is the intestine, flattened dorso-ventrally ; to 

 right and left, in the body-wall, are the lateral lines, 

 enclosing the excretory vessels and the lateral nerves ; 

 at the top and bottom of the central plane are the 

 dorsal and ventral median lines, showing the nerve- 

 fibres and the manner in which they branch out 

 towards the muscular structure. 50 : 1. (After 

 Brandes.) 



