MASTIGOPHORA 1083 



animals by the tsetse fly. The distribution of Glossina is not uni- 

 form, as they are only present in certain definite areas called fly 

 belts. Since the disease does not spread in the absence of the 

 larger wild animals, it has been proposed that all big game be 

 exterminated as a prophylactic measure. Mice and rats are sus- 

 ceptible and die in six to fourteen days after inoculation; guinea- 

 pigs are more resistant, and may show one or more relapses within 

 two to ten weeks. It has not been possible to immunize larger 

 animal's, although a certain degree of success has been obtained 

 with the smaller animals used in the laboratory. 



Cultures have been grown on artificial media, yet not so readily 

 as with lewisi and avian trypanosomes. The medium recommended 

 by MacNeal contains the extractives of one hundred and twenty-five 

 grams of meat, ten of pepton, five of salt, and twenty-five of agar 

 to the liter ; to this is added twice its volume of warm, defibrinated 

 rabbit 's blood. The blood agar slants should be soft and moist when 

 inoculated. Filtrates from cultures are not toxic, the toxin ap- 

 parently being liberated, according to MacNeal, from the body of 

 the disintegrating trypanosome. 



Trypanosoma hippicum (Darling). The disease caused by this 

 trypanosome in horses and mules has been known in Panama for 

 many years under the name of "Murrina de caderas" or "Der- 

 rengadera de caderas," the latter term being used when paralysis 

 of the posterior extremities is the dominant symptom; both names 

 indicate a weakness of the hind quarters. The symptoms are weak- 

 ness, emaciation, and, sooner or later, conjunctivitis and subcon- 

 junctival ecchymosis, and anemia. The horses and mules affected 

 are obviously weak, and while in the stall, pull back on the halter, 

 or stand with straddling hind legs. 



The incubation period in animals used for experiment is less 

 than a week, a few animals lose weight rapidly and die within a few 

 days, others live for several weeks. 



Treatment, including the use of arsenical preparations, is without 

 effect, and all infected animals should be destroyed. 



The disease is apparently transmitted directly by flies, which 

 carry blood and serum from ulcers and abrasions on infected to 

 healthy animals. 



Morphology of the Parasite. The trypanosome is sixteen to 

 eighteen microns long and two microns wide. The kinetonucleus 

 is about two microns from the posterior end, the trophonucleus 



