208 ON THE OCCURRENCE OF *' WORM-NODULES I» CATTLE 



ing fibrous capsule may vary greatly in different nodules. 

 The parasite, Onchocerca gihsoni, Cleland and Johnston,, 

 lies coiled in the worm area in such an intricate manner 

 that it is impossible to extract the female entire. The 

 small male worms may occasionally be obtained in an 

 unbroken state. These nematodes are seen to lie in a 

 definite tunnel or canal, within which they appear to be 

 capable of a slight movement. Gilruth and Sweet (1911, 

 p. 10, figs. 3, 4, 37) have figured a tunnel in which the male 

 and female worms are lying side by side. The actual 

 nodules are, of course, the result of irritation of the sur- 

 rounding cells of the host-tissue, set up by the presence 

 of the parasite. An eosinophilia is also present. When 

 the worms dies, it degenerates, becoming calcified and 

 finally breaking down, the worm area undergoing a degener- 

 ation also. This condition is more fre(juently met with in 

 older animals. The statements that tuberculosis is commonly 

 associated with this alteration are not substantiated. 



Seat of infection, etc. : — The commonest situations 

 in which the parasite occurs are the brisket and flanks 

 between Avhose muscles and in Avhose subcutaneous tissues 

 the worm-nodules lie. The affected areas have been 

 defined as follows :— (Gilruth and Sweet, 1911, p. 5, 6.) 

 " The commonest situation is the region of the brisket, 

 chiefly the triangular outline formed by the junction of 

 the ribs with the costal cartilages, especially between the 

 fourth and sixth ribs, but often extending backwards to 

 the tenth, and, at times, forward to the second rib. Fre- 

 quently they are superficial, i.e., in the subcutaneous tissues,^ 

 but more often they are situated between the posterior 

 portion of the superficial pectoral muscle and the anterior 

 part of the posterior deep pectoral, between the posterior 

 portion of the deep pectoral and the external abdominal 

 oblique, and between the panniculus and the posterior por- 

 tion of the external oblique, rarely deeper. . . The 

 other situation is the external surface of the hindlimb, 

 especially behind the femoro-tibial joint, and the groove 

 leading upward to the pelvis, anterior to the gluteus 

 maximus, and even near the angle of the haunch. While 

 occasionally superficial and readily detected, they are often 

 under the dense subcutaneous fascia lata, when they are 

 much more liable to be overlooked." They mention the 



