AX EXPERI MENTAL IXA'ESTIGATIOX OE 
TRYPAXOSO^LX LEMTSL 
By Edward Fraa'CIS. 
Assistant Surgeon, CA S. Public Health and Marine-Hospital Service. 
The great importance of a thorough familiarity' with try-panosomes 
is seen when we consider that within the past year and a half the 
recognition of trypanosomes was forced upon onr governmental medi- 
cal officers in the Philippines, where the army horses and mules were 
dying in great numbers, due to the presence in their blood of a para- 
site which the untrained eye might readily regard as a spirillum or a 
filaiia, but which proved to be the trypanosome of Surra (1). It is 
probably' best in the beginning to say something of trypanosomes in 
general. They are animal parasites (Hematozoa) of large size which 
are often found in enormous numbers free in the blood j^lasma, but 
do not invade the interior of the blood corpuscles. They manifest a 
strikingly vigorous eel- like motility as they dart among the coriDuscles, 
pushing them aside. 
The Trypanosoma Evansi is the cause of surra, a fatal disease of 
horses and mules in India and the Philii^pines. 
The Trypanosoma Brucii causes the tsetse fly' disease, or Xagana, 
which attacks the horses and cattle in central Africa. 
The Trypanosoma equinum is the cause of mal de caderas, a disease 
of horses, etc., in South America. 
Dourine, or maladie du Colt, a disease of horses and dogs, particu- 
larly' in Algeria and Spain, has been attributed to the Trypanosoma 
equiperdum. 
The Trypanosoma Lewisi is the cause of a nonfatal affection of 
wild rats, which harbor spontaneously the parasites in enormous 
numbers in their blood j)lasma. 
And now Avithin the past year we have a trypanosome of man. 
AVhether the six trypanosomes mentioned above represent really' 
distinct species or whether two or more of them will be found to be 
identical must remain for further scientiflc investigation. Morj)hol- 
logically all six have many structures in common, but they also show 
