SLEEPING SICKNESS 



879 



gony, and that division was simple and longitudinal, taking place 

 always in the circulating blood and producing transmission forms, 

 which are her short blood forms. 



These forms can be ingested by Glossina palpalis (but one has to 

 be sure that it is really palpalis, as flies apparently of this species 

 have been found by King, using Newstead's more accurate methods 

 of classification, not to be tliis species), first estabhshing themselves 

 in the posterior part of the mid-gut and then multiplying and form- 

 ing many types therein, but moving on the tenth to twelfth day to 

 the proventriculus in the form of long, slender, non-infective trypano- 

 somes, from which they find their way via the hypopharynx to the 

 salivary glands after the sixteenth day. In these glands they 

 assume a crithidial form, from which after multiplication small 

 infective trypanosomes appear after the eighteenth to twenty-first 

 da}^ — i.e., some two to five days after infection of the salivary 

 glands. 



Miss Robertson never saw any signs of conjugation or of sexual 

 forms, as described by Minchin, Gray, and Tulloch, but considers 

 the cycle in the fiy has this significance, and if so the fly is the 

 definitive host, and susceptible animals can be infected by its bite. 



Is there hereditary infection of the fly via the ova, as shown by 

 O'Farrell to take place with a crithidia in a tick ? This question is 

 so far answered in the negative. 



Is there an animal reservoir for T. castellanii ? Perhaps there is, 

 but notwithstanding Duke's experiment with an antelope, we believe 

 that no such reservoir has been proven; and this is supported by 

 the very small numbers of wild glossinse which have been found 

 to contain T. castellanii. One suspects that if there is a reservoir, 

 it must be in man himself when he becomes more or less immune 

 to the disease. 



The possibility of direct infection during sexual intercourse 

 must be remembered, in addition to insect carriage. 



There appears to be no doubt that the fly at present labelled 

 Glossina palpalis is the carrier of the disease, as all experiments 

 tend to show. 



Castellani Type of Sleeping Sickness. 



Parasite. 



Definitive 

 Host. 



Definitive 

 Reser- 

 voir. 



Infection. 



Inter- 

 mediate 

 Host. 



Inter- 

 mediate 

 Reser- 

 voir. 



Trans- 

 mission. 



Trypano- 

 soma 

 castellanii. 



Glossina 

 palpalis. 



Hereditary 

 infection 

 of tsetse- 

 flies (?). 



Short 

 salivary 

 trypano- 

 somes. 



Inocula- 

 tive. 



Man. 



Game 

 ani- 

 mals (?). 



Short 

 blood 

 trypano- 

 somes. 



Ingestive. 



