8 



general lines already known in similar cases 

 of whatever etiology. Only the study of the 

 concrete facts could furnish interesting 

 pathognomonic data. Other subjective and 

 objective symptoms of the cases of block 

 are of great value; however, let us reserve 

 them for later explanation and pass now to 

 the study of the extrasystoles. 



3. Extrasystoles. -The function of excit- 

 ability is attacked in the majority or perhaps 

 in all of the chronic cases of American tryp- 

 anosomiasis. The patients with extrasysto- 

 les are almost counted by the number of 

 infected, and such is the frequency of the 

 symptom that we use it with profit as the 

 best factor for estimating the endemic index 

 of the disease. 



Extrasystolic contractions are seen from 

 the least advanced ages to old age and the 

 number of children in whom we have found 

 this alteration is quite high, and this is also 

 a condition peculiar to trypanosomiasis. 

 However, they are not found in the acute 

 cases of ttie disease in spite of the intense 

 lesions of the myocardium in the initial 

 phases of the infection when the parasites 

 are found in great abundance in the heart 

 muscle. 



It is clear from this that the extrasys- 

 tole indicates rather a process of diffuse 

 myocarditis and is more closely related to 

 fibrous changes in the muscle than to the 

 acute inflammation that is found in the 

 early stage. As regards its origin these heter- 

 ogenetic pulsations can be referred to the 

 ventricle, to the auricle and to Tawara's 

 node; here, however, as is general for this 

 symptom, the ventricular extrasystoles pre- 

 dominate and are observed in a very high 

 percentage relatively to the others. The 

 auricular extrasystoles are somewhat rare, 

 also those of nodal origin. 



The inconstancy of the symptom in some 

 cases should be emphasized, and this often 

 makes its observation difficult and may 

 lead to wrong conclusions from its absence. 

 Some factors, whose intervention must be 

 profited by in doubtful cases, especially in- 



fluence its appearance. In the first place is 

 the attitude; the extrasystoles aie frequent 

 principally in the dorsal decubitus, and many 

 patients who show regularity of the pulse 

 in the vertical position present extrasystol- 

 ic contractions when lying down. Next 

 come effort, fatigue and emotion. Often we 

 only succeed in finding the symptom by caus- 

 ing forced movements of the patient or by 

 producing sudden emotions. And in spite of 

 the interference of the factors referred to 

 the individuals are not rare in whom the 

 extrasystoles are periodic, and only appear 

 from time to time, with intervening phases 

 of regular rhythm. 



The frequency of the symptom in dif- 

 ferent patients or in different phases of the same 

 case is very variable. Sometimes the extra- 

 systoles are separated and only appear 

 at long intervals in the tracings; others, 

 however, present themselves with great fre- 

 quency, being repeated in every cardiac 

 cycle or two in the same cycle, giving the 

 tracings the classic appearance of bigemin- 

 ism and trigeminism. 



It is of greater importance to note the 

 prolonged sequence of extrasystoles with 

 absence of compensating rest between the 

 interposed beats, present in the beginning 

 and end of the group-, aud this is charac- 

 teristic of the crises of symptomatic parox- 

 ysmal tachycardia in this disease. We have 

 various observations of this symptom which 

 show the occurrence of the attack at the 

 moment when we were taking the tracings ; 

 however, it is possible to judge of its fre- 

 quence from the histories given by the pat- 

 ients with extrasystoles, who, as a rule, 

 refer to transient crises of palpitation with 

 rapid beating of the pulse and appreciable 

 and very inconvenient contractions of the 

 heart. 



Taking into consideration the moment 

 of the diastolic phase of the cycle in which 

 the extrasystolic contraction appears, we 

 must emphasize here the presence of inter- 

 polated extrasystoles in many cases. Rela- 

 tively rare in the alterations of excitability 



