374 



PARASITES OF ANIMALS 



disease, terminating in death," without any suspicion on the part 

 of the practitioner as to the nature of the malady. Instructive 

 cases of this form of helminthiasis are given by Messrs Littler, 

 Wyer, Harris, Meyrick, Litt, Percivall, Tindal, Walters, 

 Brett, Aitken, Mead, Clancy, Baird, Mercer, Wright, Seaman, 

 Hepburn, and others. 



Second only in clinical importance is the little four-spined 

 strongyle (8. tetracanthus) . The sexes, often seen united, are 

 nearly of equal size, the largest females reaching nearly ". 

 They infest the caecum and colon, and have been found in all 

 varieties of the horse, ass, and mule. The worm occurs in 

 immense numbers and is a true blood-sucker. Its presence 

 occasions severe colic and other violent symptoms, often proving 

 fatal to the bearer. As already announced, in connection with 

 my account of the tapeworms of the horse, this little worm 

 may produce a virulent epidemic (epizooty). In the sexually - 



immature state the worm occu- 

 pies the walls of the large intes- 

 tine, where it gives rise to con- 

 gestion, ecchymosis, inflamma- 

 tion, and the formation of pus 

 deposits. The species is readily 

 recognised by its bright red 

 color, by the four conical spines 

 surrounding the mouth, by the 



FIG. 63. Larvae of Strongylus tetracanthus. a, two neck-bristles, and by the 

 of the intestine (natural size); , * 



from the walls 



4, the same (enlarged) ;*, an injury ; c, younfjer long three-lobed hood of the 

 specimen (m sit*} ; d, the same (enlarged). Ori- . 



g lual - male, the posterior three- cleft 



ray having a rudimentary or fourth branch attached to its 

 outer edge. In some specimens sent to me by Mr Whitney, I 

 found this supplementary process fully twice as long as 

 Schneider has represented it. 



From the earliest times this entozoon has been confounded 

 with the palisade worm. Rudolphi and several of his successors, 

 and also in recent times Ercolani and Colin, regarded this worm 

 as the progeny of Strongylus armatus. During my earlier 

 examinations I likewise fell into the error of describing the 

 immature worm as representing a new species. The parasites 

 described by me as Trichonemes (T. arcuata) were identical 

 with those which Prof. Dick had previously described as 

 " worms at different stages of growth," in his MS. sent to Dr 

 Knox, 1836. Parasites of this kind were described by Dr 



