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SCIENCE 



[N. S. Vol. XXXVIII. No. 986 



diseases, on account of its near chemical 

 relationship 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 elim- 

 inated from the body to be successful in 

 the larger animals and man, and so we de- 

 vised 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. The leucocytes eat it up and 

 transform it slowly into some soluble form, 

 taking, in a horse, for instance, four days 

 to dispose of one dose, and the effect of this 

 is much more profound and lasting than 

 that of the salts. But some trypanosomes 

 always escape, since one dose is never suffi- 

 cient for cure. In rats with nagana, in 

 which the trypanosomes by the fifth or 

 sixth day may number 3,000,000 per cubic 

 millimeter of blood, the minimum number 

 of doses for cure has been found to be four, 

 and with this dosage it is possible to cure 

 100 per cent, of rats. So there is still some 

 hope. 



It is interesting in this connection to re- 

 member what Bacon, whose death, you 

 know, was due to an experiment he under- 

 took to prove the preservative action of 

 intense cold upon animal bodies, says, 

 "Laying aside, therefore, all fantastic no- 

 tions concerning them, I fully believe, that 

 if something could be infused in very small 

 portions into the whole substance of blood 

 ... it would stop not only all putrefac- 

 tion, htit arefaction likewise, and be very 

 effectual in prolonging life." His vision 

 was prophetic! 



The bird trypanosomes are very much 

 larger than the mammalian variety, are 

 very dense and move much more slowly. 



An example of an organism very closely 

 allied to the trypanosomes which is only 



found in fishes' blood, and is called a Try- 

 panoplasma, has two flagella, and the 

 micro-nucleus is very large. They ar& 

 probably transferred by leeches, but very 

 little is yet known of them. 



There are other flagellated organisms 

 which may appear in the blood and live 

 there as accidental parasites. There is a 

 kind of inflammation of the intestines in 

 reptiles (in the large sense) which causes 

 the mucosa of the intestine to become per- 

 meable, so that some of the organisms which 

 live in the intestine are able to get into the 

 blood and live there. The only mention of 

 these organisms in the blood is by Dani- 

 lewsky, who in 1889 found hexamitus in the 

 blood of a frog and tortoise. When in the 

 blood they appear to excite a general 

 cedema and ascites. I have found them 

 now in nine cases. These are interesting as 

 showing the power of adaptation to new 

 surroundings possessed by these parasites. 



I now come to the intracellular parasites. 



Schaudinn thought that the bird try- 

 panosomes had an intracellular stage, and 

 if this were so they would form a bridge 

 between the extracellular parasites, of 

 which I have shown you types, and the 

 intracellular parasites we are about to con- 

 sider. But Schaudinn seemed, with his 

 very brilliant attainments, to want a little 

 more ballast of medical earth-knowledge. 

 His work on this point has not been con- 

 firmed, and he was probably misled by a 

 double, or even treble infection, so that we 

 must think of these intracellular parasites 

 as quite distinct from the others. 



I will take first the Plasmodium prcecox, 

 the cause of the malaria in birds, as this 

 parasite is of great historical interest; for 

 it was Ross's work on this organism and 

 his discovery of the rest of its life-cycle in 

 the mosquito, which enabled him — on ac- 

 count of the great likeness between this and 

 the parasite causing human malaria — ^to 



