After having studied the new parasi- 

 te's morphology I started to work on 

 its biology. In repeated experiments, I 

 obtained new laboratory infection not 

 only in monkeys of the genus CalUthrix, 

 but also in guinea-pigs, rabbits and pup- 

 pies. These infections were obtained in 

 some cases by tJie stinging of the insect but 

 mostly by inoculation of the flagellates 

 taken from its intestine. Lengthy experi- 

 ments thus allowed me to characterise 

 the trypanosomc as a new species and 

 to established the part played by the 

 barbeiro in its transmission. Besides 

 this I made sure of the pa- 

 thogenic properties of the Irypanoso- 

 me whicli brought about the death, in 

 a variable period, of small laborato- 

 ry animals, generally by septicaemia and 

 witliout the disappearance of the para- 

 site from the peripheric circulation. The 

 remainder of the experiments I carried out 

 related to the double evolutive cycle of the 

 trypanosome in the vertebrates and in 

 the insect transmitter, the forms of evo- 

 lution in the intestine of the barbeiro, 

 the artificial cultivation of the proto- 

 zoon etc. 



And it was then after having 

 acquired ample knowledge of the para- 

 site, in its morphology, general bio- 

 logy and pathogenic action that I 

 undertook the second part of mj»^ re- 

 search-work that was to give the more 

 remarkable results as regards human 

 pathology. 



To the new species of trypanosome 

 I gave the name of Trypanosoma Cruzi, 

 in honom- of my unforgettable leader, 

 to whom I owe everything in my scien- 

 tific career, and who in tliese studies 

 was to me the most broad-minded of 

 counsellers: to the impersonation of 

 scientific capability and kindness, al- 

 v.-ays ready to let me partake of the be- 

 nefits of his knowledge and to harbour 

 me in the warmth of his friendship. 

 What little work has been accomplislied 

 hy me in my professional career 



is more his than mine, and 

 what there may be of useful in 

 this work I attribute with pride and sin- 

 cerity to the value of his teaching and 

 to the example of his high faith, to 

 that decisive sway of his strong per- 

 sonality and great abnegation upon ali 

 those who had the good-fortvme to en- 

 counter him during their lifetime and 

 to reap the benefits of that influence that 

 shaped their careers. 



This is tlie exact truth concerning 

 the discovery of Trypanosoma Cruzi, 

 known up to this point only as a para- 

 site of a vertebrate of unknown species 

 and transmitted by the sting of an in- 

 sect. The latter was determined as Tria- 

 loma megista BURM. by Dr. ARTHUR 

 NEIVA who in lengthy studies descri- 

 bed its whole biology. 



In tliis first period of our work the 

 most interesting point was the observa- 

 tion of a hemipteron as a transmitter 

 of parasites. This observation was far- 

 reaching as regards general biology and 

 was by itself a scientific fact of real 

 importance. 



I will now proceed to describ^^ the 

 discovery of Trypanosoma Cruzi in man 

 and the observation of the new disease. 



Returning to the triatoma-infested re- 

 gions, it became my object to ascertain 

 the vertebrate host of Trypanosoma Cruzi^ 

 inasmuch as the monkeys and laboratory 

 animals I had worked upon were all o£ 

 them experimentally infected and did not 

 demonstrate the ordinary host of the para- 

 site. 



The difficul(j' of interpretation of 

 the local clinical cases together with, 

 the supposition based on careful obser- 

 vation and lengthy research-work of the 

 existence of a patliological condition that 

 escaped identification with any establi- 

 shed disease, facts which I had 

 reflected on for some time and which 

 made me suppose an miknown etiologic 

 cause, became the starting-point for the 

 work I then undertook. To add to this waa 



