TRYPANOSOMIASIS EXPEDITION TO THE CONGO 
In the majority of animals which have died we are unable to say definitely that trypanosomiasis was 
the sole cause of death. Very frequently an intercurrent affection has occurred which, the animal's 
vitality having become impaired, has caused death. We would instance in rats broncho-pneumonia, 
caseous lung disease, and enteritis. In rats which have survived a few to many months it is exceedingly 
rare to find a single parasite, 1 nor has the negative blood appeared to be infective. Experiments are 
being conducted along these lines. In the majority of cases those rats which have been negative for 
months die without the presence of trypanosomes being again recognized. In some cases, however, rats 
which have been negative for months have at death once more shown parasites. As instances of this the 
following experiments are given. 
Rat 95a 1 (' Q ' strain) was inoculated on March 17, 1903, from horse Experiment 87 ; incubation 
period, eight days ; parasites were found at irregular intervals and in small numbers. On September 1 3, 
1903, a single parasite to a whole cover-slip preparation was seen, and the animal continued negative 
until its death on March 24, 1904, three hundred and sixty-five days after infection. At the necropsy a 
few parasites were found in the heart. Animals inoculated from it have not yet shown the infection. 
Rat, Experiment 89' (' Lammin ' strain). Inoculated February 26, 1903, from rat 26 ; incubation, 
eighteen days. Trypanosomes were present in its blood until April 21. From that time parasites were 
never seen except on the following dates, Jul}- 27, September 7, and November 1, 1903, until its death 
on March 15, 1904, three hundred and sixty-six days after infection. At the necropsy complete red 
hepatization of the whole of the left lung was found. The left pleural cavity contained over five cubic 
centimetres of slightly" yellowish clear exudate containing one parasite to three fields. Animals inoculated 
with this exudate became infected, and from these sub-inoculations we have been able to infect a goat 
Experiment 518, and a monkey, Experiment 517. 
We have observed that animals with extraordinary numbers of trypanosomes in their blood usually 
exhibit some lesion which tends to impair their vitality. The following experiment is a good example of 
this. A rat, 279a ('Gunjur' strain), inoculated on December 30, 1903, from a guinea-pig became 
positive on January 7, 1904. From that time until it was killed on March 22 the parasites were 
constantly present in increasing numbers in its blood. At the necropsy caseous lung disease was very far 
advanced, involving both lungs. Its blood on examination showed trypanosomes in countless uumbers. 
Two rats, two mice, three guinea-pigs, one rabbit, and a puppy were all inoculated intraperi:oneally with 
heart-blood. Twelve hours later the mice and rats, the rabbit and two guinea-pigs were found to be 
positive, the rats and mice having as man} - as three to eleven to a field, the rabbit two hundred and forty 
to the cover-slip preparation, and the two guinea-pigs eight to the cover. The puppy did not show 
parasites in its blood until five days later. 
Very little, if an}-, immunity is conferred by infection with Trypanosoma gamblense. The two 
following experiments are of interest in this connexion. 
1. A piebald rat was inoculated directly from Mr. Q. by Dutton and Todd on November 3, 1902, 
Parasites were found in its blood on November 12, and again on February 27, 1903. After this the 
blood was always negative. On November 23, 1903, it was reinoculated intraperitoneally from a rat 
('Gunjur' strain) showing very numerous trypanosomes. It became infected, and on December 9 its 
blood was swarming with trypanosomes. Death took place on December 26. 
2. A monkey {Macacus rhesus) infected by Annett from H. K. (Dutton's original case) in 1902 
recovered, its blood being non-infective to rats. On January 29, 1904, it was reinoculated (Experiment 
311) from a rabbit (' Gunjur' strain), and became infected (see above). 
As one would expect, there is no transmission of immunity to offspring. Several of the young rats 
which we have infected have been born from parents which either were infected at the time or had 
1. This is also the case in other animals. See chimpanzee experiment. 
2. Dutton and Todd, he. cit. 
3. Ibid. 
