746 Mr. Henry George Plimmer [May 2, 



in a crustacean. The microfilarige were discovered by Demarquay in 

 1863. Many of them show a remarkable periodicity, some appearing 

 in the blood at an exact hour at night, and some in the day, for which 

 phenomenon there is at present no satisfactory explanation. 



Some are short, and some long, and some are encapsuled, others 

 not. Filarise cause various diseases, probably elephantiasis, and 

 certainly enormous varicosities of the lymphatics, chyluria, chylous 

 dropsy, Calabar swelling, and certain tumours. 



We now come to the Trypanosomes. They are flagellated 

 organisms, which are the cause of many deadly diseases in men and 

 animals ; such as sleeping sickness, nagana (or tsetse-fly disease), 

 surra, mal-de-caderas, dourine, and others. They are transferred from 

 animal to animal by biting flies, fleas, lice and leeches, in which the 

 sexual part of their life-cycle takes place. The first one was seen in 

 the blood of a frog by Gluge in 184-2. 



A type example is T. Lewisi in the blood of a rat. This was 

 discovered by Lewis in 1878, and is found in about 2 5- -2 9 per cent 

 of wild rats. Some die, but most recover and become immune ; it 

 is a very specific parasite, and cannot be transferred to any other kind 

 of animal. 



The T. Brucei, causing nagana or tsetse-fly disease, probably 

 exists in the wild game of South Africa, much as the T. Lewisi 

 does in the wild rats, but when it is carried by the tsetse-fly to 

 domesticated animals it kills them one and all in enormous numbers. 



The T. Gambiense, which causes sleeping sickness, was first seen 

 by Button in 1902, and is carried by another species of tsetse-fly. 



Nature attempts to fight against these invaders by phagocytosis. 

 The parasites, however, multiply so rapidly that this method of 

 attack is not very effectual ; it can only l)e so in very early infec- 

 tions, and probably it then often is, that is, before the parasite has 

 had time to start dividing. At the present time the question of 

 trypanosomosis amongst man and animals is, for many countries 

 which have colonies, of the greatest economic importance, so that 

 a great deal of work has been done in the attempt to find a cure, A 

 great many drugs, new and old, have been tried, and some good has 

 been done. The first drug which was found to be of service was 

 arsenic, first in simple and then in complex combination, and the 

 Sub-committee of the Royal Society, formed for the purpose of 

 supervising experiments in this direction, suggested the trial of 

 antimony in these diseases, on account of its near chemical relation- 

 ship to arsenic. 



This has given better results than arsenic, and a commission is at 

 present at work in Africa, in the Lado district, trying its effects on a 

 large scale. We found that the salts of antimony were too rapidly 

 eliminated from the body to be successful in the larger animals and 

 man, and so we devised a very finely divided form of the metal itself 

 which we put directly into the circulation, and this has given, so far, 

 the best results. Tlie leucocytes eat it up and transform it slowly 



