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IV. — Tlie Filaria immitis. Amended Anatomical Details. 



By F. H. Welch, F.E.C.S., Assistant to Professor of Pathology, 

 Army Medical School, Netley. 



In my i^aper* descriptive of the thread- worm, F. immitis, the Canine 

 Haematozoon, among other anatomical details of the parasite two 

 conclusions are arrived at which subsequent dissections have proven 

 to require modification ; I refer (a) to the assumed coecal termination 

 of the intestine and consequent absence of anal aperture,t and (h) to 

 the merging of the two uterine channels diverging from the vagiua 

 into one membranous tube continuous with the convoluted ovarian 

 tubes at the tail end of the female worm 4 



Further examination of more recent specimens has shown me 

 that these details do not correspond with the facts since brought to 

 light, and as they are important points in the anatomy of the worm 

 I hasten to correct them. 



Termination of the Alimentary Canal. — Plate XXX., Fig. 2, 

 female worm, and Plate XXXII., Fig. 16, male worm, illustrate a 

 coecal termination of the canal. However, on getting rid of the 

 cucaneous envelope of the tail end of the parasite by maceration and 

 dissection, and taking away most of the muscular parietes with the 

 contained ovarian coils, I have traced the intestinal canal, contracted 

 from the average 4^^th inch to yoVoth inch in diameter, from 

 beyond the assumed coecal termination of the delicate tube to within 

 T^oth inch of the terminal end of the worm, and when tension was 

 brought to bear on this short unexplored portion the canal separated 

 invariably from the inside of the muscular tip with a ruptured end 

 and dimpling in of the external surface. The walls of the intestine 

 are so thin that when collapsed it is easy to overlook the ^ube, 

 which is mainly indicated by its dark contents ; and when these stop 

 abruptly, accompanied by a reduction in calibre of the canal, it is 

 not difficult to be misled in favour of a coecal termination. The 

 presence of much dark granular material in the peri- visceral cavity 

 at the tail end prevented the tracing of the delicate tube through it 

 with absolute certainty, yet considering that up to within xio^h inch 

 from the tail end it could be unquestionably followed, and that a 

 ruptured end invariably ensued on tension being applied to this 

 short obscured portion with indrawing of the outer surface, I think 

 that a bhnd ending to the alimentary canal may be fairly negatived. 

 Hence I conclude that an anal aperture is present in this blood 

 parasite, and to make the sketches in accordance with these details 

 it becomes necessary to extend the tubes, marked a and jp respec- 

 tively in Plate XXX., Fig. 2, and Plate XXXIL, Fig. 16, to the 

 extreme tip of the tail. 



* 'Monthly Microscopical Journal,' Oct. 1st, 1873. 

 t Ibid., p. IGO. X Ibid., p. 161. 



