644 



NA TURE 



[October 26, 1905 



in others with doubtful results. This is, however, only 

 what might be expected in view of the diversified difficul- 

 ties which must necessarily arise. 



There has been a veritable flood of malaria literature 

 of recent years, including an annual volume of " Atti della 

 Society per gli studi della malaria," the series commencing 

 in 1900, which has come to us from Italy. Mosquitoes 

 have received an immense amount of attention, after being 

 much neglected in the past. The number of genera and 

 species and their classification have become subjects to 

 bewilder all but specialists. 



The important discoveries on sleeping sickness ushered 

 in by the researches of Castellani, a pupil of this school, 

 have been confirmed and extended by Bruce and his 

 collaborators of the sleeping sictcness commission. The 

 relation of the flies belonging to the genus Glossina fb the 

 transmission of the trypanosomes is being actively studied, 

 and many important questions we must hope are nearing 

 their solution in connection with this most fatal malady. 

 A contribution has just come to hand from Gray and 

 TuUoch with regard to the multiplication of the parasites 

 in Glossina, indicating that the belief recently expressed 

 is warranted, namely, that the parasites undergo a cycle 

 of development within the insects. Of importance in their 

 bearing on the question of the development of trypano- 

 somes in other than their vertebrate hosts are the investi- 

 gations of Schaudinn on Trypanosoma noctuae in Culex, 

 those of Brumpt on certain trypanosomes of fishes which 

 undergo their cycle of development in leeches, and those 

 of Prowazeck on the rat trypanosome, which he has demon- 

 strated undergoes development in the rat louse {Haemato- 

 pinus spinulosus). 



Of recent discoveries, the one which to me appears to 

 carry the greatest weight is that of Novy and McNeal. 

 They have been the first to obtain pure cultures of 

 Protozoa, maintaining trypanosomes of different species 

 alive in vitro for many generations. There is no telling 

 whither the methods they have given us may lead ; thev 

 directly stimulated Leonard Rogers to experiments wherein 

 he succeeded, by an ingenious method of his own, in 

 cultivating another protozoon, the Leishmania, obtained 

 from cases of kala-azar. 



The work on the tick-transmitted diseases known as 

 the piroplasmoses (redwater, &c.) occurring in cattle, 

 sheep, horses, and dogs has been pursued in various parls 

 of the w^orld with great activity. The results appear to 

 me to indicate, what I believe also holds for human malaria 

 parasites, that we shall in time learn to distinguish 

 different parasites which we at present consider to repre- 

 sent single species. 



The investigations of Dutton and Todd on tick fever in 

 the Congo Free State, announced in February, have gone 

 to prove that this disease is transmitted by a tick 

 (Ornithodoros savignyi) after it has infected itself with 

 blood containing the Spirochjeta. This has been confirmed 

 by Koch, if we may rely on what has appeared recently 

 in German new-spapers. It is, however, quite premature 

 to assume that African tick fever and European relapsing 

 fever are due to one and the same species of Spirochaita ; 

 in fact, it is highly probable that this is not the case! 

 although the report in question refers to the Spirocha^ts 

 as one species. In relapsing fever in Europe the bed- 

 bug (Cimex) has long been suspected to be a carrier of 

 the infective agent, a probability which was considerably 

 heightened by Karlinski's observation of motile Spiro- 

 chaetse in the bodies of the insects up to thirty days after 

 they had fed on relapsing fever blood. Schaiidinn', more- 

 over, informs me that he has observed the multiplication 

 of the Spirochaeta obermeieri in Cimex. These observ- 

 ations, following closely upon those published by 

 jMarchoux and Salimbeni, are of greatest interest and 

 practical import. The last named authors demonstrated 

 that a fatal disease of the fowl in Brazil is due to a 

 Spirochaeta which is transmitted through the agency of a 

 tick (Argas miniatiis), and this is capable of conveying 

 the disease even six months after feeding on infected blood. 

 These Spirocha5t,-e multiply in the tick, and are present 

 in large quantities in its bodv cavitv throughout this 

 period. These observations are verv suggestive, since they 

 demonstrate the long persistence of the "parasites in their 

 earners, and render it probable that thev will be found 

 >'0. 1878, VOL. 72] 



to be harboured much longer. Finally, the finding this 

 year of Spirochaeta pallida in syphilis by Schaudinn and 

 others in man, and by Metschnikoff and Roux in experi- 

 mentally infected apes, cannot escape a passing notice. 



It is of some interest to note that the close blood- 

 relationship existing between the apes and man, demon- 

 strated independently by means of the precipitins by 

 Griinbaum and myself, served as a direct incentive for the 

 experiments of Metschnikoff and Roux, Lassar, and 

 Neisser, which proved that human syphilis is communicable 

 to the chimpanzee and ourang outang. 



Of interest has also been the further discovery this 

 year of a number of new protozoal parasites in the blood 

 of different animals, in addition to numerous new species 

 of Trypanosoma. I refer to new forms called " Leuco- 

 cytozoa " because they inhabit the white blood corpuscles 

 of their vertebrate hosts. Leucocytozoa were first dis- 

 covered by Bentley in dogs in India, and were described, 

 without sufficient mention of this fact, by James, .'\nother 

 species has been found by A. Balfour in the rat (.U. decu- 

 maniis) in Khartoum ; and lastly, W. S. Patton informs 

 me that he has found a species in the squirrel {Sciurus 

 palmartim) in India, and apparently observed developmental 

 forms thereof in a louse. Balfour has, moreover, described 

 a new Hcemogregarine occurring in the jerboa {jaculus 

 jaciilus)^ and Graham-Smith in our laboratory has found 

 another new endoglobular parasite in the mole. This by 

 no means exhausts the " finds " of this year, but it will 

 suffice to show that British workers are doing their share 

 in furthering our knowledge in this regard. 



Of the diseases due to Vermes I can say but little. The 

 discovery of Catto's Schisostomum in this laboratory is 

 familiar to you all. It is interesting to note, following on 

 the experiments with Ankylostonta duodenale by Loos, 

 proving that the embryo worm can infect by penetrating 

 through the skin, that Boycott in London and Tenholt in 

 Germany have confirmed the fact this year in two experi- 

 ments conducted on medical men who volunteered for the 

 purpose. 



Again, it is apparent that the subject of immunity in 

 relation to protozoal diseases is proving to be one of great 

 difficulty, and the results hitherto obtained indicate that 

 new methods will have to be devised if the problem is to 

 be solved from a practical, and still more so from a scien- 

 tific, standpoint. It is also obvious in this connection that 

 the problems before us can only be solved by animal experi- 

 ment, and this accentuates the need of our giving an in- 

 creasing amount of attention to comparative pathology as 

 we push on toward the alleviation of the ills to which 

 our own flesh is heir. 



Many matters have necessarily been left untouched, in- 

 cluding even such important diseases as yellow fever and 

 Malta fever, on which active work has been done. My 

 object has been to seize upon a few salient facts with the 

 view of showing how much has been accomplished within 

 a short period, and how great are the opportunities of the 

 workers in this school who are destined to labour in new 

 fields in different parts of the world. Perhaps what I 

 have said — in no spirit of presumption — will serve as an 

 incentive to some of my hearers. Let me conclude with 

 some wise words from the Talmud : — 



" The day is short and the work is great. 

 It is not incumbent upon thee to complete 

 the work, but thou must not therefore 

 cease from it." 



THE MECHANICS OF THE ASCENT OF 

 SAP IN TREES.' 

 'T'HE following remarks, relating to one of the most 

 pow-erful and universal of the mechanical operations 

 of organic nature, are based mainly on the .numerous 

 experimental results reported in Dr. A. J. E wart's recent 

 memoir. = Their chief object is to assert the view that 

 we are not compelled to suppose the sap, in the column 

 of vessels through which it rises, to be subject to the 

 great actual pressure, amounting in high trees to manv 

 atmospheres, that is sometimes postulated. It is hardly 



1 By Prof. J. Larinor, Sec R.S. Paper received at the Poyal Society on 

 June 2g. 



= A'<y. Soc. Proc, vol. I.\riv. p. 554 ; Phil. Trnns., B, vol. cxcviii. p. 41 



