142 



NATURE 



[August 4, 1910 



to that of the earth, it will fall in about one mile in 

 the first year. If it continues to describe a nearly 

 circular spiral, it will fall in less and less each revolu- 

 tion, but the revolutions take less and less time, and 

 in equal times it will fall in more and more. Such a 

 sphere will reach the sun in something- of the order 

 of 45,000,000 j'ears. But the rate of falling in is 

 inversely as the radius, so that a sphere i/iooo cm. in 

 diameter will fall in looo miles in the first year, and 

 will reach the sun in 45,000 years. 



There is no doubt that there are such bodies m our 

 system. We have clear evidence of their existence 

 when they perish as shooting stars in our atmosphere. 

 Also there seems no way to avoid the conclusion that 

 they are all spiralling in to the sun and will ultimately 

 reach him unless their career is cut short by some 

 intervening planet. How, then, are we to account for 

 their existence in our system to-day ? Whatever limit we 

 may assign to the age of the earth as a habitable globe, 

 we must assign to the sun some vast number of millions 

 of years, vast enough to have allowed him long ago 

 to draw to himself all the specks of dust in his system. 

 How is the supply renewed? Is interstellar space 

 inhabited by scattered meteorites? .^re they brought 

 in bv comets which have become disintegrated? And 

 so light pressure raises once more an old and still 

 unsolved problem. 



A NEW TRYPANOSOME PARASITIC IN HUMAN 

 BEINGS.' 



THE terrible mortality caused by sleeping sickness 

 in Africa, and the knowledge that this deadly 

 disease is caused by a species of trypanosome, has 

 directed the attention of the general public, as well 

 as of scientific and medical men all over the world, 

 to these blood-parasites. The frequent occurrence of 

 trypanosomes in the blood of vertebrate animals of 

 all classes has long been known to zoologists, but this 

 fact was regarded as little more than a scientific 

 curiosity until Bruce, scarcely fifteen years ago, 

 showed that a species of trypanosome, since named 

 after him {Trypanosoma brucii), was the cause of the 

 dreaded tsetse-fly disease of domestic animals in Africa, 

 and followed this up by his discoveries, in the present 

 century, with regard to the nature and transmission 

 of sleeping sickness. 



No little sensation was created, therefore, when it 

 was announced by Chagas about a year ago ' that 

 he had discovered a new species of trypanosome, 

 named by him Trypanosoma cruzi, in human blood in 

 Brazil. A full account of this parasite, its develop- 

 ment, and mode of transmission, has now been pub- 

 lished by Chagas, with numerous illustrations, and 

 it proves to be a form no less interesting from the 

 purely zoological than from the medical standpoint. 



The manner in which this parasite was discovered 

 is remarkable. Chagas found that in the province of 

 Minas Goraes the houses, especiallv the thatched huts 

 of the poorer classes, were infested by bugs (Fig. i) 

 of the species Conorhinus mcgistiis, voracious blood- 

 suckers of large size and nocturnal habits, responsible 

 for much loss of sleep, as well as of blood, to the 

 unfortunate inhabitants. Some of these bugs were 

 collected and brought to Rio de Janeiro, where they 

 were dissected and examined in the laboratorv of the 

 Instituto Oswaldo Cruz, and were found to contain in 

 their digestive tracts numerous flagellate organisms 

 resembling in form and structure the genus Crithidi-i. 

 When such bugs were allowed to feed on experimenta 



1 " Nova ttinano'omiaie humana." By C. Chai;as, Memoriae do Initi- 

 tiito Oswaldo Cruz I., 1Q05. Pp. 1513-218 ; plates ix-xiii and 10 te.\t-figures. 

 (Portuguese and German text.) 



2 See the Bulletin of the Pasteur Institute for May 30, 1909, p. 453. 



NO. 2127, VOL. 84] 



animals, namely, marmosets (Callithrix pcnicillata) and 

 guinea-pigs, they infected them with trypanosomes, to 

 the effects of which the marmosets succumbed in about 

 two months, the guinea-pigs in five to ten days. 

 Aiter this surprising result, Chagas returned to Minas 

 Geraes and examined the blood of human beings in the 

 zone infested by the bugs, and found several cases of 

 human beings infected with similar trypanosomes. 

 Thus the course of the discovery of this parasite has 

 been the exact opposite to that of the progress of our 

 knowledge of sleeping sickness ; there the disease was 

 thoroughlv known long before it was found to be 

 caused by a trypanosome, then the mode of trans- 

 mission was discovered, and the complete life-cycle of 

 the parasite has not yet been worked out ; here the 

 transmitting insect was first known, then the parasite 

 itself was discovered, and, last of all, it was found to 

 occur in human blood, with the result that the life- 

 cycle of the trypanosome has been investigated in 

 considerable detail, but very little is known of its 

 effects in their clinical aspect. 



The few cases of infected human beings observed 

 bv Chagas have not been followed out by him to 

 their end as yet. He finds the effects of the parasite 

 to be most marked, however, in children, amongst 

 whom it appears to cause severe mortality. The chief 

 symptoms are anaemia, oedema, general or localised, 

 enlargement of the lymphatic 

 glands and of the spleen, 

 and functional disturbances, 

 especially of the nervous 

 system, leading in some 

 cases to imbecility. .-\ 

 tendency to arrest of develop- 

 ment, resulting in pro- 

 nounced infantilism, was 

 also noticed. According to 

 information collected, the 

 fatal termination of the 

 disease was frequently at- 

 tended by convulsions, re- 

 garded locally as the cause 

 of death, and sometimes by 

 dropsy in the last stages. p,^ 



The life-cycle of the para- 

 site, as described by Chagas, 



shows some peculiarities not yet known in 

 any other species of trypanosome. In the vertebrate 

 host it exhibits three phases, which may be termed 

 conveniently the adult, the multiplicative, and the 

 growth phase respectively. 



In the adult phase, the organism is free in the 

 blood-plasma, and has the typical trypanosome- 

 structure (Fig. 2, a). It shows, however, a di- 

 morphism which Chagas regards as sexual. One 

 form, regarded as male, is more slender, with a larger 

 kinetonucleus and a more elongated trophonucleus ; 

 the other, regarded as female, is broader, with smaller 

 kinetonucleus and rounded trophonucleus. 



These adult trypanosomes in the peripheral blood 

 wore never observed to multiply by fission, a fact 

 which the author seems to consider remarkable, 

 doubtless from the standpoint of studies upon patho- 

 genic trypanosomes, though it may be pointed out 

 that the same is true of the common trypanosomes of 

 vertebrate animals, especially those of birds and 

 fishes. Chagas has discovered that the multiplication 

 takes place by a process of multiple fission or 

 "schizogony" in the lung. Hence he founds pro- 

 visionally a. new genus, Schizotrypanum, for this 

 species. It remains to be seen how far such schizo- 

 gony is peculiar to this parasite. The only salient 

 difference between the multiple fission of Schizotry- 

 panum cruzi and that of the common Trypanosoma 



