57^ 



NATURE 



[August 20, 1908 



mometer with a pressure of i atmosphere at about 

 20° K. Corrected to the absolute scale the best value 

 would appear to be 4'5° K. The triple point, if it 

 exists, is certainl)' below i cm., perhaps below 7 mm., 

 at which, by corresponding' states, the temperature 

 would be about 3° K., and the liquid remains very 

 mobile. 



Liquid helium has a density of 015, which gives 

 ^i a value of 000017, about twice that which has been 

 assumed before from then Unown properties and used 

 in calculations. From this, again, the critical pres- 

 sure must be about 2 to 3 atmospheres, so that 

 hflium under 5000 would correspond with carbon 

 dioxide under 100,000 atmospheres. At the boiling 

 point the ratio of vapour to liquid density is i : 11, 

 which indicates a critical temperature of not much 

 more than 5° K., and a critical pressure of about 2'3 

 atmospheres. Lastly, the value of a will be about 

 o'oooo5, the smallest value known, but a most in- 

 teresting confirmation of van der Waals's contention 

 in 1873, that there must be some attraction between 

 the molecules of all substances. 



Fr.'\ncis Hyndman. 



THE ETIOLOGY OF TRYPANOSOMIASIS. 



T N a communication to the Paris Academy of 

 •*■ Sciences on February 24, some remarkable dis- 

 coveries concerning the development of pathogenic 

 trypanosomes in tsetse-flies are brought forward bv 

 M., E. Roubaud, member of the Mission Fran^aise 

 d'Etudes de la Maladie du .Sommeil. Experimenting 

 with four species of pathog'enic trypanosomes, namely, 

 Trypanosoma gaiubicnsc, T. dimorphon, T. briicci, 

 and T. cazalboui, and with Glossina palpalis, Roubaud 

 found that iminediately after the fly has fed on the 

 blood of an infected animal, its' proboscis contains 

 blood in which the trypanosomes are moving actively. 

 In a very short time, however, the trypanosomes 

 attach themselves to the wall of the proboscis and 

 undergo changes of structure, becoming Herpeto- 

 monas-like, with the kinetonuclcus in front of the 

 trophonucleus. The undulating membrane has dis- 

 appeared, and the flagellum, as the organ of fixation, 

 is greatly thickened, so as to resemble a small stalk 

 to the body. These changes are complete in five 

 niinutes after ingestion of the blood. The attached 

 parasites at first exhibit active movements of the body, 

 but soon become quiescent ; no phenomena of con- 

 jugation could be observed, either before or after these 

 changes. But the parasites multiply actively in this 

 situation, forming little tufts or colonies, so that at 

 the end of one hour they have become excessively 

 numerous; they are found attached to the internal face 

 of the labrum, sometimes chiefly at the base of the 

 proboscis, in other cases along its whole leneth as 

 far as the point. When observed in the salivary fluid 

 they appear immobile, but when treated with serum or 

 with physiological salt-solution they vibrate rapidly 

 .uid may become free, in which case they swim with 

 the flagellum forward and the hinder part of the 

 body rigid, thus differing greatly in appearance from 

 the original trypanosome-form. ']"he free parasites 

 have a great power of attachment, and when under 

 observation they may fix themselves firmly to the 

 slide. 



The author regards this development as a tem- 

 porar)' culture or " culture d'attente " of the para- 

 sites. Both by observation and experiment he shows 

 that the forms in the proboscis are not derived from 

 trypanosomes regurgitated from the digestive tract of 

 I he tsetse. T. hriicci was found to die out without 

 multiplication in the intestine of Glossina palpalis in 

 a short time. The culture in the proboscis was found 

 NO. 2025, VOL. 78] 



to persist beyond forty-eight hours in the case of T. 

 brucei, and for five or six days in the case of the other 

 three species of trypanosomes. Only about ten per 

 cent., however, of the tsetses fed on infected animals 

 developed a culture of the trypanosomes in the pro- ' 



boscis. On the other hand, the power of multiphing 

 in the proboscis was found to be a specific relation j 



between the trvpanosomes and the tsetse. 



These observations lack as yet the crucial test of an 

 experimental infection by means of the proboscis- 

 culture, but nevertheless they throw great light on 

 the problem of the transmission of pathogenic trypano- 

 somes. It has been shown by previous experimenters 

 that the transmission is effected by the direct or 

 mechanical method, and all attempts to prove experi- 

 mentally an indirect or cyclical mode of transmission 

 have given negative results. That being so, it w'as 

 difficult to understand w-hy the power of direct trans- 

 mission should be possessed, apparently, by tsetse- 

 flies alone, and not bv other biting insects to an eaual 

 degree. Roubaud 's observations show that the pathr- 

 genic trvpanosonies have a quite specific power of 

 adapting themselves to the salivary secretions of the 

 tsetse, and thus explain the peculiar relation between 

 these flies and the spread of diseases caused by trypano- 

 somes in Africa. Moreover, a very important new- 

 line of investigation is indicated by the author's 

 discoveries. E. A. M. 



NOTES. 

 About a year ago Sir William Ramsay and Mr. A. T. 

 Cameron announced that they had observed the production 

 of the alkaline metals and lithium in solutions of copper 

 salts submitted to the action of the radium emanation, and 

 concluded that in the presence of the emanation copper 

 underwent a degradation into the elements potassium, 

 sodium, and lithium. In the current number of the 

 Compies rendus of the Paris Academy of Sciences, Mme. 

 Curie and Mile. Gleditsch give an account of the attempts 

 they have made to repeat this experiment. They first 

 point out the extreme difficulty of obtaining chemical pro- 

 ducts free froni lithium. This metal was found in distilled 

 water and in nearly all the reagents. If a reagent, free 

 from lithium, is allowed to stand in a glass vessel, traces 

 of this metal are found after some time. Even fused quartz 

 is not a safe material, since both opaque and transparent 

 quartz were found to contain notable amounts, the latter 

 furnishing the larger proportion. The experiments had 

 therefore to be carried out in such a manner that the solu- 

 tions came in contact with platinum only ; the water and 

 the acids necessary for the experiment were re-distilled from 

 platinum and preserved in platinum bottles, and after this 

 treatment no lithium could be detected in the residue from 

 25 c.c. of the nitric acid, 25 c.c. of hydrofluoric acid, and 

 250 c.c. of water. The quantities of copper and radium 

 emanation were about the same as those used in the 

 original experiment. The salt residues obtained weighed 

 0-4 and 0-5 milligram, the control experiments giving 03 

 and 0-2 milligram. Spectroscopic examination of this 

 residue showed it to consist of salts of sodium with a little 

 potassium ; the presence of lithium could not be proved. 

 Direct experiments on known mixtures of sodium and 

 lithium sulphates showed that the amount of lithium pre- 

 sent in the residue, if any, must be less than o-exio-" 

 milligrams. In conclusion, the authors state that they 

 have been unable to confirm the experiments of Messrs. 

 Ramsay and Cameron. It is impossible to state that no 

 trace of sodium or lithium is formed in this experiment, 

 but they consider that the fact of the formation of these 

 elements cannot bo considered as established. 



