808 THE FLAGELLATA 



On adding some immunized rat serum or the normal serum of certain other 

 animals (especially fowl, horse, dog, sheep, or rabbit) to defibrinated blood 

 or serum containing Trypanosomes agglomeration takes place in a few 

 minutes and is often complete. The rosettes may then collect together 

 forming enormous masses visible to the naked eye. The parasites constituting 

 these masses are motile. Disagglomeration is sometimes observed (Laveran 

 and Mesnil) : the trypanosomes which were instantaneously agglomerated 

 by the serum again become free in a few hours. While the property of 

 agglomeration appears rapidly in the blood of immunized animals, the 

 paralyzing property (leading to the immobilization of Trypanosomes whether 

 agglomerated or not) is only seen in hyperimmunized animals. 



Experimental inoculation. Rats are readily infected with Trypanosoma 

 leivisi, but with the exception of the guinea-pig in which a very short and 

 abortive infection occurs no other animals are susceptible. Infected blood 

 or a culture will reproduce the disease when inoculated into the peritoneal 

 cavity, into the blood stream, sub-cutaneously or even into the stomach of the 

 rat. Rats become infected by consuming the blood of infected rats (Francis : 

 not confirmed by Laveran), 



The most certain method of infection is by intra-peritoneal inoculation. During 

 the first 3 days following the inoculation the parasites multiply in the peritoneal 

 cavity and numerous reproduction forms can be seen. Then the trypanosomes 

 disappear from the peritoneal cavity, but appear in the blood where they rapidly 

 multiply : multiplication forms are however less numerous in the blood than they 

 are in the peritoneal cavity. At the end of a week the trypanosomes cease to 

 multiply in the blood, and for a period varying from 20 days to 4 months only 

 slender adult parasites are seen (latent period). 



The number of parasites in the blood varies. Sometimes there are as many as 

 1 to every 2 or 3 red cells. 



Generally speaking, the presence of Trypanosomes in the blood of the rat 

 is unaccompanied by any symptoms of disease ; in some cases, however, the 

 infection may prove fatal (Jiirgens, Francis, and others). 



Immunity. Rats in which parasites appeared in the blood after a first 

 inoculation of trypanosomes never show a blood infection on subsequent 

 inoculation. The serum of rats which have been inoculated several times 

 with trypanosome blood is prophylactic, and if inoculated at the same time 

 as the parasites into the peritoneal cavity of a normal rat the trypanosomes 

 do not pass into the blood (Kempner and Rabino witch) : it fails however 

 to cause the elimination of trypanosomes from the blood of infected rats 

 during the latent period (Laveran and Mesnil). 



The serum of immunized rats has powerful agglutinating properties and 

 rapidly leads to rosette formation when diluted from five to fifty times. 



Trypanosomes in rodents other than rats. 



Jolyet and de Nabias have found trypanosomes in the blood of four out of ten 

 rabbits examined in Bordeaux. The trypanosome-infected rabbits were generally 

 thin and wasted, and suffered from diarrhoea. The trypanosomes were long, and 

 including the flagellum measured 30-36/x ; the body was nucleated, cylindrical in 

 the centre, pointed behind and terminated anteriorly in a flagellum : the undulating 

 membrane was very narrow and could only be seen after staining. In fresh blood 

 the parasites were highly motile. 



Trypanosomes have also been found in rabbits by other observers (M. Nicolle, 

 Petrie), as well as in guinea-pigs (Ktinstler), mice (Dutton and Todd), squirrels 

 (Donovan, Laveran), ground-squirrels (Chalachnikow), etc. 



