336 TRYPANOSOMA CAZALBOUI [CH. 



species and may subsequently prove to be identical, but at 

 present it is impossible to unite them without increasing the 

 confusion of the subject. 



The incubation period is usually about seven days. The 

 course of the disease is variable and may be either acute, 

 subacute, or chronic. In the former case, cattle may succumb 

 in as short a time as eight days after infection. The average 

 duration of the malady is about two months, being terminated 

 by the death of the infected animal, but in some cases the dis- 

 ease lingers on for more than a year, and recoveries are not 

 unknown. 



The parasites are usually rare in the peripheral circulation, 

 but often increase in numbers previous to the death of the 

 host. 



Morphology of T. cazalboui. The movements of the living 

 parasite are very active and it frequently darts across the field 

 of the microscope. 



It is a monomorphic species and its dimensions are very 

 constant ; in stained specimens about 24 microns in length, by 

 1-5 to 2 microns in breadth. The trophonucleus is oval and 

 situated about the middle of the body, whilst the distinct 

 and spherical kinetonucleus is situated very close to the 

 rounded posterior extremity. The undulating membrane is 

 not markedly folded, resembling that of T. lewisi ; the fiagel- 

 lum is always free at the anterior extremity. 



Division is of the usual longitudinal type. 



Mode of infection. The principal agents for the transmis- 

 sion of Souma are tsetse-flies, four species of which, viz., 

 G. palpalis, tachinoides, longipalpis and morsitans, have been 

 proved capable of carrying the infection. In addition, Bouffard's 

 experiments have shewn that Stomoxys may serve as a direct 

 carrier (vide p. 362). 



The distribution of Souma seems to shew that Glossina pal- 

 palis is the usual intermediate host, and Bouffard found that 

 in Upper Guinea this species was commonly infected with T. 

 cazalboui. Experimentally, both G. palpalis and G. tachinoides 

 have been proved to be very liable to become infected when fed 

 on an animal containing the trypanosomes in its blood, for 



