TR YPA NO SO MI 



mention as occurring between the kinetonucleus and the trophonucleus 

 appears to have been also seen by Prowazek. Asexual reproduction may be 

 summarized into reproduction with longitudinal division and reproduction 

 with rosette formation and encystment after some interchange between the 

 kineto- and tropho-nuclei, followed in due course by increased power for 

 longitudinal division. Battaglia describes a process of sporogony with the 

 formation of macro- and micro-gametocytes, and of macrogametes and micro - 

 gametes, and a similar reproduction has been described by Pricolo. Carini's 

 cyst-like bodies in the lungs are considered by Delinois to be a coccidium, 

 Pneumocystis cavinii. 



In the Invertebrate. — The rat-flea, Ceratophyllus fasciatus, is the true carrier 

 of L. lewisi, as was first demonstrated by Nuttall, and the rare development 

 which may take place in louse Polyplax spinulosa is more of the nature of a 

 natural culture than a proper development. The development in the flea 

 has been studied by Swellengrebel and Strickland, and more recently by 

 Minchin and Thompson. 



When the flea ingests blood containing the flagellates, they pass directly to 

 the mid-gut, where they enter the epithelial cells, inside which they attain 

 a large size and undergo multiplication in a peculiar manner by forming a 

 large spherical body containing a number of tropho- and kineto-nuclei, and 

 developing flagella, while the original flagellum still remains attached, but is 

 subsequently lost; and then the cytoplasm divides into the daughter trypano- 

 somes, which are now set free, and, passing into the rectum, become crithidial 

 forms by the kinetonucleus travelling past the trophonucleus towards the 

 flagellum. These crithidial forms attach themselves to the wall of the rectum, 

 and shorten into Leishmania-like forms without flagella or without free flagella. 

 These in their turn develop into trypanosome forms, which pass forwards 

 into the mid-gut. 



The intracellular stage is at its height about the end of the first day after 

 infection ; the rectal stage begins during the second day, the trypaniform types 

 pass into the mid-gut towards the end of the fifth day; and the flea is infective 

 in about six days after its own infective meal. 



The 191 5 work of Minchin and Thompson may be summarized as follows:— 



L. leivisi is transmitted from rat to rat by the rat-flea Ceratophyllus fasciatus, 

 but infection does not occur by the flea-bites, but is contaminative by the rat 

 licking from its fur or skin the moist faeces of infective fleas containing the 

 final propagative form, or by eating the fleas. 



The cycle of development is as follows: — The flea sucks the blood of an 

 infected rat, and so acquires the trypanosomes, which require a minimum 

 of five days to attain the infective stage, which is a small trypanosome which 

 does not penetrate the salivary glands, but remains in the digestive tract, 

 from which it escapes in the faeces, which are taken into the mouth of the rat 

 while licking the fur. The flea remains infective for a long time, but does not 

 pass the germ on to the next generation. After infection some five to seven 

 days elapse before the trypanosome appears in the rat's blood, in which it 

 multiplies till the eleventh to thirteenth day after infection. 



In the louse, Polyplax spinulosa, the life-cycle has been studied by Prowazek, 

 who finds that the micro- and macro-gametocytes undergo first a reduction 

 of the trophonucleus from sixteen chromosomes to four, and that then the 

 microgametocyte gives rise to only one microgamete, which fuses with the 

 macrogamete, forming an ookinete. This becomes a trypanosome by the 

 separation of the kinetonucleus from the synkaryon. The flagellum projects 

 from the posterior end, which the kinetonucleus now leaves, and, taking the 

 flagellum with it, proceeds towards the anterior end, thus forming the undu- 

 lating membrane. Gregariniform non-flagellate forms also appear, which 

 penetrate between the epithelial cells. Prowazek failed to infect rats by 

 the bite of the louse, but this has been done successfully since. Swellengrebel 

 and Strickland find that the development in the louse is very irregular and 

 not to be compared with that in the flea. 



Cultivation. — Cultural experiments have been carried out successfully by 

 Novy and McNeal on a medium prepared by mixing agar and defibrinated 



