Cause of W'orni-No'iules in Cattle. 27 



1. — Direct Infection. 



Tn test so far a.^ possible whether any intenir^diate host be neces- 

 sary, a well-formed nodule containintj a livino; parasite was removed 

 from a cow containinfj; a fair number of nodules, and transplanted, 

 under all proper conditions of asepsis, etc., to the subcutaneous tissue 

 behind the shoulder of a calf born and reared at the Institute. Eight 

 months later this animal was killed. The nodule was found firmly 

 adherent to the skin, flattened and souieAvhat smaller in diameter than 

 previously, and surrounded by an intimate capsule of diffuse new 

 connective tissue, which covered it so effectually that it would have 

 l)een quite overlooked had not the exact spot of the transplantation 

 been known. Tlie parasite was dead, and calcified in pinhead areas. 

 Evidently, therefore, as mitrht be expected, the parasite will not live 

 in other than the individual host in which it has developed, and 

 probably cannot leave the nodule once the latter is formed, and so 

 re-infect the same animal or pass out and infect another. Also, the 

 larvae from this living nodule had every opportunity and sufficient 

 time to infect the new host. ;uid to form nodules, since well-formed 

 nodules have been found in (j-8 months old calves, so that any possi- 

 bility of direct infection without the iuti^i uit-diaiion of another liust is 

 negatived, as one would have expected. 



2. — 1 iiferniediatiuii of Soil. 



A quantity of earth from a cow-yard in North Queensland, wherein 

 badly infected cows rested eveiy night, was imported here. It was 

 examined ver}^ carefully for any sign of larvae or adult Onchocerca, 

 both before and after moistening, and after incubating for some days, 

 with negative results. 



The soil was spread evenly over a deep layer of ordinary soil in a 

 pen in which a young locally-bred calf was placed. The pen was a 

 warm one, and the soil was kept moist for some time after deposition. 

 Seven months afterwards, the calf was killed and most carefully 

 examined, and showed no trace of nodtdes, or of adult parasites in any 

 part of the body, or of larvae either in the blood or in the subcutaneous 

 areolar tissue, glands, muscles, or intermuscular tissue of the brisket ; 

 so that, at all events in this ca.se, where all the conditions were as 

 favourable as they could possibly be, infection by intermediation of 

 the soil alone, is absolutely negatived. 



3. — Interrnediafion of the Louse and Infection by Direct Contact. 



A calf referred tO' in the previous paper, to which lice had been arti- 

 ficially transferred after being allowed to feed on a restricted area 

 inoculated with numerous larvae, died some nine months after trans- 



