108 



3. Experiments with H. megastoma: — 



(a) Larvae placed in the skin of the horse — 



Proboscides of Musca domestica heavily infested with larvae 

 were placed in three incisions in the skin of the mare and removed 

 from five to six hours later, when there was present a marked 

 inflammatory oedema of the tissues. One area was removed five 

 hours after inoculation for the purpose of microscopic examination. 

 Larvae were found to have made their way into the subcutaneous 

 tissues, where leucocytes had commenced to surround 'them. 



The other two sites were left for further observation. After 

 inoculation the primary tumefaction reached a maximum in about 

 forty-eight hours, and had a diameter of from 6 to 7 cm. This 

 gradually subsided, and in nine days' time one site was removed, 

 when there was present a granuloma about the size of a small 

 walnut. Microscopic examination showed an intense infiltration 

 of the tissues with eosinophiles, hyperplasia of the fixed cells, the 

 formation of multinucleated cells, and the presence of necrotic 

 areas containing degenerating larvae. 



The other granuloma persisted for about three weeks, when 

 it gradually disappeared. 



The experiments were repeated on the pony. Proboscides 

 were placed in three incisions in the skin and removed from five 

 to six hours later, when there was marked inflammatory oedema of 

 the tissues. This increased during the next twenty-four hours, 

 but had very much decreased in forty-eight hours after inoculation. 



One area was removed six hours after inoculation. Micro- 

 scopic examination showed that the larvae had made their way 

 into the subcutaneous tissues, where they were surrounded by 

 leucocytes. 



The other two areas were left for further observation. In 

 forty-eight hours after inoculation the swelling had almost dis- 

 appeared, and in three or four days' time there was little or no 

 thickening of the tissues. 



(b) Larvae added to the conjunctival sac — 



Larvae were added to the conjunctival sac (near side) of 

 the mare. Twenty-four hours later no reaction had been produced. 

 In three or four days' time excessive lacrymatipn was present. In 

 a further three days the conjunctiva was injected and somewhat 

 swollen. Small yellowish "tubercles" were to be seen on the 

 membrana. These persisted for over a Aveek, but in a fortnight's 

 time had entirely disappeared. Epiphora continued, however, for 

 about six weeks. 



The experiment was repeated on the pony with exactly the 

 same results. 



( c) Larvae placed on a scarified area of skin — 



Larvae were placed on three scarified areas of the skin of the 

 mare. Larvae were added to one of the scarified areas on three 

 consecutive days. In no case was any reaction produced. 



This experiment was repeated on the pony, two scarified areas 

 being made. No reaction was produced. 



(d) Larvae placed on a moistened area of skin — 



Larvae were placed on two moistened areas of the skin of 

 the mare. No reaction was produced. 



The experiment was repeated on two areas of the skin of the 

 pony with the same result. 



