THE TRYPANOSOME OF CHAGAS' DISEASE 823 



gametogony in contradistinction to what he believes to be simple schizogony 

 taking place in other parts of the body (vide infra). 



In the lungs the trypanosome loses its undulating membrane, the two ends 

 curve towards each other like a crescent and unite ; the female parasites 

 then shed the blepharoplast and in both the male and female parasites the 

 chromatin divides into eight secondary nuclei giving rise to eight merozoites, 

 those derived from female parasites having a single nucleus, the others having 

 both a nucleus and a blepharoplast connected by a fine thread of chromatin. 

 These merozoites (the precursors of the gametes found in the circulating 

 blood) then enter a red cell and develop into typical trypanosomes. These 

 forms have been found in man, monkeys (Callithrix), cats and dogs but are 

 very uncommon in guinea-pigs. 



To demonstrate the changes above described Chagas recommends that a guinea- 

 pig should be infected with a Conorrhinus and that 1-2 c.c. of the blood of this first 

 animal should be inoculated intra-peritoneally into a second guinea-pig which 

 should be killed 5 or 6 days later. 



In other structures. Within the cells of certain other tissues, and notably 

 in cardiac and striated muscular tissue and in neuroglia cells, the trypanosome 

 multiplies, according to Chagas, by simple schizogony and gives origin to a 

 great number of daughter parasites each having a nucleus and centrosome. 

 In the cells of the central nervous system the young trypanosomes may 

 proceed to the flagellated stage. The infected host cell is reduced to a mere 

 envelope and the contents with the exception of the nucleus are destroyed. 



In the insect carrier. In the mid-gut of Conorrhinus megistus the blepharo- 

 plast approaches and perhaps blends with the nucleus, the undulating mem- 

 brane disappears, the parasite becomes rounded and then multiplies rapidly 

 by division. The daughter parasites become flagellated, the flagellum taking 

 origin from the blepharoplast. In the posterior cylindrical portion of the 

 mid-gut numerous flagellated crithidial forms are found. 



On two occasions Chagas found trypanosomes in the body cavity and in 

 the salivary glands of the bug. The latter no doubt represent the forms 

 which are inoculated when the insect bites a susceptible animal. 



Cultivation. The parasite grows easily on Novy and MacNeaPs blood- 

 agar. The cultivation forms are similar to the forms found in the bug 

 round forms, rapidly dividing pear-shaped forms and crithidial forms. The 

 parasite can almost always be sub-cultivated twice. 



Etiology. Chagas concludes that the bug Conorrhinus megistus does not 

 play a purely mechanical part in the transmission of American trypanosomiasis. 

 The bug is not infective for at least a week after the infecting meal. 



In Chagas' opinion there are two different forms of development in the bug. 

 One the last stage of which is represented by the crithidial forms in the mid- 

 gut and which is always seen after the insect is fed on infected blood is 

 without importance. The other which is very imperfectly known probably 

 represents the true cycle. 



Detection of the parasite. Blood films may be prepared and stained by 

 Giemsa's and Rosenbusch's method but it is better to inoculate the blood into 

 the peritoneal cavity of a guinea-pig. 



9. Trypanosomes in birds. 



Danilewsky [in 1888] was the first to give a description of trypanosomes 

 in birds (Trypanosoma avium). Kecent work has shown that there are 

 several species of avian trypanosomes (Laveran, Button and Todd, Hanna). 



A large number of birds are known to be infected ; for instance owls, roller- 



