INSECTA 183 



6 mm. long, with a longitudinal mouth-opening at the anterior end of 

 the ventral surface. This mouth-opening is surrounded by a chitinous 

 ring, and upon either side of it are two claws, each mounted upon 

 a slighter curved basement rod. The body is transparent, the cuticle 

 finely annulated ; at the posterior edge of each of the eighty to ninety 

 rings is a fine, recurved tooth. Of the internal organs it is possible to 

 make out the intestinal canal, the genital organs, and sometimes 

 the nervous system. The male and female are distinguished by 

 the position of the genital pore ; in the male it is placed upon the 

 ventral surface, in the median line, behind the seventh annulation ; 

 in the female it is near the posterior end, immediately in front of 

 the anus. These larval forms when found are frequently dead, the 

 body being in a state of fatty or chalky degeneration. As in the 

 case of calcified cysticerci and echinococci, the portions of the parasite 

 which resist the degenerative process longest are the claws and 

 basement rods. These will be seen if the calcified parasite is treated 

 with some acid solution. The sexually mature parasites inhabit the 

 nasal cavities of the carnivorous and herbivorous mammals. They 

 are present in 6 to 10 per cent, of dogs. 



II. INSECTA. 



(1) Bed-lugs (Cimex lectularius) . For purposes of examination 

 specimens should be chosen which have fasted for some time. They 

 should be cleared and, after very careful treatment with potassium 

 solution, they should be examined under the microscope. Insects 

 which are gorged with blood should be kept until the intestinal 

 contents have become absorbed. 



The body of the bug is quite flat and is composed of a head- 

 piece, together with three thoracic and eight abdominal segments. 

 The surface, both of the body and of its appendages, is covered with 

 numerous simple, pointed, chitinous hairs and with coarse bristles, 

 one edge of which is serrated. The four-jointed antennae are situated 

 at each side upon the front of the head; behind them are the eyes, 

 furnished with several strongly arched corneas. Proceeding from 

 the ventral surface of the frontal part of the head is the four-jointed 

 rostrum, which is recurved towards the abdominal surface. The three 

 thoracic segments are quite distinct. The anterior segment, which 

 is also the largest, is deeply, incut to allow of the insertion of the 

 head, and has the appearance of a half-moon, with rounded horns 

 directed forwards. The second thoracic ring is smaller than the 

 other two ; when viewed from above it is triangular in shape, with 

 the apex pointing posteriorly. At its sides are the scale-like rudi- 

 mentary wings, which extend backwards as far as the first abdominal 



