
AucGuUsST 12, 1915] 
NATURE 
663 

Tue RESERVOIR OF T. gambiense (CONGO SLEEPING- 
SICKNESS). 
Besides man, who is probably the most important 
reservoir of the virus, native cattle and the antelope 
living on the lake-shore in Uganda were found to 
harbour the parasites in their blood. 
The prophecy that the fly would become harmless 
shortly after the natives were removed from the lake 
shore has unfortunately proved wrong, and before the 
islands are repopulated some other measure will have 
to be taken to get rid of the fly danger. 
Group. B.—Tue T. pecorum Group. 
I.—T. pecorum. 
The first of this small group, which only consists 
of two species, is T. pecorum. It is probably the most 
important trypanosome disease of domestic animals 
in Central Africa. 
Morphology. 
Fig. 2 shows the general appearance of the trypano- 
some. It is the smallest of all the African pathogenic 
trypanosomes, varying from g to 18 microns in length, 
with an average of 14 microns. 
Animals Susceptible to T. pecorum. 
In regard to the animals attacked by this trypano- 
some. This is essentially a disease of the herds: 
horses, donkeys, oxen, goats, sheep, and pigs, all fall 
victims. 
Taste V.—The Average Duration of Life, in Days, of 
Various Animals Infected by T. pecorum. 







] 
> | >| Nr 
\z alba lrellorlow (2 (ges 
= elaleis|s/atsae® 
C i 
= aes 
oe Dee een | ea | 
Average duration in days... .-» | 87?) r2n2] 55.| 2t |129 | 48 | 4x | 33 
Number of animals employed [exateaaleson) ox lene | 570], Sol x0 

The Percentages of Recoveries in Various Animals 
from T. pecorum Infection. 
-- [ 80/1/35 | 12:]> 0 On ax o| oa 
5 lag i7ol 1 | rr 1 63:1 51 10 
Percentages 355 tn oo 
Number of animals employed 



This trypanosome does not seem to be very fatal 
to horses, mules, or donkeys. In Nyasaland there 
was no opportunity of testing it on horses, but out of 
five donkeys four recovered. Two-thirds of the cattle, 
and seven-eighths of the goats, succumbed. 
THE CARRIER OF T, pecorum. 
The chief carrier of T. pecorum is G. morsitans. 
In Nyasaland, this parasite was the commonest of the 
trypanosomes with which G. morsitans was infected. 
There were fifty-six experiments, and 10,081 tsetse-flies 
(G. morsitans) were employed. In the fifty-six ex- 
periments T. pecorum was found forty-six times, more 
than twice as often as T. brucei. Nine monkeys, 
thirty-four dogs, and thirty-five goats were infected. 
This gives a proportion of 4-6 per 1000 flies infected 
with T. pecorum. 
Tue Cycle oF DEVELOPMENT OF T. pecorum IN 
G. morsitans. 
This trypanosome belongs to Group B, in which 
development takes place first in the gut and then 
passes forward into the labial cavity of the proboscis, 
and finally reaches the salivary duct or hypopharynx 
where the trypanosomes revert to the original blood 
form and become infective. There is no infection of 
the salivary glands. 
-NO. 2389. VOL. 95] 



Tue Type or TRYPANOSOMES FOUND IN THE INFECTED 
FLIES. 
Fig. 5 represents the developmental forms of T. 
pecorum found in labial cavity of G. morsitans. The 
first seven. figures represent early forms in the labial 
cavity. These were seen adhering singly by their 
flagella to the labrum. 
The next group contains the ordinary forms found 
clinging by their flagellar ends to the labrum. It 
will be seen that they have assumed the crithidial 
stage, a stage which seems to be a sine quad non in 
the final stages of the cycle of development of all the 
pathogenic trypanosomes, and the interpretation of 
which is still obscure. The small blood forms are from 
the hypopharynx of dead infective flies. They repre- 
sent the final stage in the cycle of development and are 
the only infective forms. On the same figure are seen 
drawings of the labrum and hypopharynx of a_ fly 
infected with this trypanosome. While the labial 
cavity is seen to contain clusters of large ribbon-like 
trypanosomes, the hypopharynx is swarming with the 
vA 
= 
(\i 
oa | 
4 
EM 
a 
we 
pe 
NII SI ee 

Fic. s.—Developmental forms of J7yfanosoma pecorum found in the 
labial cavity and hypopharynx of intected flies. a, Labrum. 4, Hypo- 
pharynx. 
small infective forms. From these drawings the ease 
and facility with which a tsetse-fly can infect an animal 
will be readily understood. 
IIl.—T. Simiae. 
This species of trypanosome is remarkable for 
the virulence it displays towards the monkey and the 
domestic pig, killing these animals in an incredibly 
short period of time, whereas it is harmless to oxen, 
antelope, dogs, and the smaller experimental animals. 
Curiously enough it affects goats and sheep, although 
oxen and antelope escape. 
In the whole range of the trypanosome diseases of 
animals there is surely nothing so striking as the 
rapidly fatal action of T. simiae on the domestic pig: 
In nine experiments the average duration was only 
5:3 days. This not from the time of the appearance 
of the trypanosome in the blood, but from the date 
of the infection. Further, this rapid action is not the 
result of an exaltation of virulence by numerous 
passages through the pig, but natural to the trypano- 
some. 
Another interesting point in regard to this species 
| is that, so far as is known, the warthog is the only 
