WORM NODULES IX AUSTRALIAN CATTLE. 337 



Although there is no sheath present the transverse striations of the 

 surface of the body of the larva may be sometimes clearly seen. 



The movements of the larvae may be well studied in the fluid 

 from a fresh nodule. Under such conditions their movement 

 is seen to be sinuous and also vvhip-Hke, certainly progressive, and 

 at times rapidly so. 



In our preHminary examinations we constantly observed, 

 on careful incision of the nodule without injury to the adult 

 parasite, a shght oozing of the serous fluid from the worm-area. 

 Examination of this fluid in the majority of cases revealed the 

 presence of free larvae ; only when the parasite was cut were eggs 

 detected. It was further noted that usually scrapings from just 

 within the periphery of the fibrous tissue, when examined micro- 

 scopically, would show the presence of free larvae. These observa- 

 tions are confirmed by sections of worm nodules. It is remarkable 

 however, how comparatively few of these larvae are to be found 

 external to the parasite within the tunnels, even when the larvae 

 are singularly numerous in the dense capsule. That these larvae 

 are not squeezed into the fibrous tissue during the process of 

 removal or handling, or carried by the knife during sectioning, 

 or confined to one particular part, is shown by a number of serial 

 sections of a large piece of the peripheral wall of the largest nodule 

 showing no trace of adult parasite. In these sections the larvae 

 are seen to be very numerous, and just as numerous near the 

 periphery as elsewhere (fig. 30). 



Although frequently found lying in close proximity (fig. 31), 

 in no instance have we been able to demonstrate their presence 

 in a blood vessel ; often, however, they may be seen within lymph 

 spaces, and it seems to us probable they reach the blood stream 

 by the lymph channels rather than by piercing the much thickened 

 walls of the blood vessels. Like Cleland and Johnston, we have 

 failed to detect any larvae in the blood of infected animals, even 

 by examination of large quantities after centrifugaHsing. We 

 suggest that the arteritis, which is such a marked feature in the 

 histology of the large nodules {see fig. 30), is probably due to the 

 irritation caused by the presence and movements of the larvae. 



Within the nodule, even twenty-four hours after the death of 

 the host, living larvae may almost invariably be detected. It 

 is probable from the following evidence that they are not capable 

 of living many days in the free state within the living host. As 

 a result of numerous subcutaneous injections of enormous numbers 

 of freely motile larvae, eggs, etc., into cattle, examination of 

 aspirated fluid, twenty-four hours later, often showed that most 

 of the larvae had disappeared ; slight movement of some of the 

 remaining larvae was present, but motihty had disappeared in the 

 majority. On the second day, when the fluid was again aspirated, 

 movement of the very few remaining larvae had entirely ceased. 

 Rarely are eggs found twenty-four hours after injection of such 

 fluid. While this evidence is, of course, not conclusive, it indicates 

 a comparatively brief history of the larvae in the host of the adult. 



