106 



about twenty hours later, the proboscides were removed and the 

 wound again protected by a covering of adhesive plaster. There 

 was a marked swelling around each wound and a collection of pus 

 in the wound. The purulent discharge completely disappeared 

 twenty-four hours after the removal of the proboscides, but the 

 tumefaction of the tissues persisted. In seven days' time a hard 

 granuloma about twice the size of a pea was present at each site. 

 One site was removed for microscopic examination, and the other 

 left for further observation. Microscopic examination showed 

 marked infiltration of the tissues with eosinophils, hyperplasia 

 of the fixed cells, and the formation of multi-nucleated cells. Only 

 one necrotic area was detected, but no larvae could be seen associ- 

 ated with this. No larvae could be found in any of the sections 

 made. The other area left for further observation gradually 

 disappeared. 



This experiment was repeated in every detail on the pony. 

 Two small granulomata resulted. One removed twelve days after 

 inoculation showed the same histological picture as the one from 

 the mare, but no necrotic areas or larvae were detected in any of 

 the sections. 



These experiments were carried out during September, when 

 the weather had become warmer. 



As the leaving of the proboscides in the wound for twenty 

 hours had produced a purulent discharge, it was decided to con- 

 siderably reduce this time in future experiments. 



About six weeks later four proboscides were placed in a wound 

 in the skin of the mare. These were removed from five to six 

 hours later. There was a marked swelling present, the area hav- 

 ing a diameter of 4 cm. The tissues were very tense, and there 

 was some blood-stained exudation from the wound. The swelling 

 increased during the next twenty-four hours, but in another 

 twenty-four hours it was much reduced. Seventy-two hours after 

 inoculation only a sight thickening was detected. The site was 

 removed for microscopic examination. In sections the larvae were 

 found to have penetrated the tissues for some distance from the 

 line of incision in the skin. They were surrounded by leucocytes, 

 the nuclei of which showed fragmentation and pyknosis. There 

 was oedema of the tissues, accumulation of leucocytes in small 

 areas and around the blood vessels. There was infiltration of the 

 tissues with eosinophiles. 



During December the same experiment was repeated on the 

 pony. Two wounds were each inoculated with three proboscides, 

 which were removed six hours later. One site was removed six 

 hours after inoculation. Microscopic examination showed that 

 there was dilatation of the vessels with oedema of the tissues. 

 The tissues were infiltrated with polymorphs and eosinophiles. 

 Larvae were found some distance from the site of inoculation and 

 surrounded by leucocytes. 



The other area was removed ten days after inoculation. There 

 was present a hard nodule about the size of a Barcelona nut. 

 Microscopic examination showed the usual inflammatory reaction 

 with giant-cell formation. There were a few necrotic areas pre- 

 sent, with which were associated degenerating larvae. 



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



An area of the skin of the pony was lightly scarified, and two 

 proboscides placed on the moist surface. The experiment gave a 

 completelv negative result, healing taking place without any tume- 

 faction of the tissues. 



