Supplement to ''Nature^' May 3, 1906 



IX 



tude, we should like to have seen the essentially vector 

 nature of the subject made more manifest, and at 

 intervals enforced by examples drawn from physics 

 and mechanics. There seems no good reason why 

 in elementary text-books of trigonometry practical 

 applications should in the main be confined to the 

 ship-tower-fiagstaff type of examples. 



(4) The text-book on engineering mathematics by 

 Mr. H. H. Harrison comprises chapters on arith- 

 metic, algebra, trigonometry, mensuration, logar- 

 ithms, squared paper, and the calculus. The presen- 

 tation of the subject by the author is crude and unin- 

 teresting, no examples are provided for practice, and 

 the book cannot be recommended for any class of 

 student. 



TROPICAL MEDICINE. 

 Lectures o)i Tropical Diseases, being the Lane Lec- 

 tures for 1905 delivered at the Cooper Medical 

 College, San Francisco. By Sir Patrick Manson. 

 Pp. viii-l-230. (London : Constable and Co., Ltd., 

 1905.) Price ys. 6d. net. 



TROPICAL pathology no doubt owes much of its 

 fascination to the fact that new diseases, or the 

 causes of old diseases, have only within the last de- 

 cade been completely elucidated, and that every year, 

 if not every month, fresh facts appear and fresh 

 subjects of inquiry suggest themselves. Thus almost 

 before the atiologv of sleeping sickness was fully 

 elucidated, students of tropical pathology were given 

 a fresh subject of inquiry from the discovery of the 

 cause of the dreaded " tick fever "' of Tete on the 

 Zambesi, and of other parts of tropical Africa. 

 When the interest in the .Anophelina? and Stcgomyia 

 fasciata had somewhat waned, the tropical pathologist 

 had his attention diverted to tsetse-flies, and then 

 again the hue and cry was in the direction of ticks, 

 especially in Africa towards Ornithodorus mouhala, 

 the transmitter of the spirochete of " tick fever." 



In India the malariologist must have recently re- 

 ceived a severe shock to find that many of his most 

 familiar cases, which he designated " malaria 

 cachexia with enlarged spleen," are in all probability 

 due to an entirely new parasite, or at least the para- 

 site can be found in the organs of such cases. In 

 tropical pathology .Africa has provided many of these 

 novelties, but, in the opinion of medical men who 

 have travelled widely in tropical .\frica, there is not 

 now much probability left of the production of a com- 

 pletely " new " disease. We do not, of course, imply 

 that manv minor discoveries do not remain to be 

 made, and, indeed, even great ones, such as the 

 causes of yellow fever and beri-beri ; and to the in- 

 vestigator who is content with elucidating minor 

 problems these fascinating lectures will afford 

 numerous examples of the kind of work that still 

 remains to be done. 



But a word of caution is perhaps necessary ; for 

 the reader is presented with a host of interesting sug- 

 gestions and speculations, and unless he advances 

 cautiously and weighs these carefullv in the light of 

 experience, he may well take the phantom hypothesis 

 for fact, for it would be possible in this particular 

 NO 1905, VOL. 74] 



branch of pathology to adduce examples where hypo- 

 thesis simply has actually retarded the acquisition of 

 knowledge. We would prefer rather to see the in- 

 vestigator laboriously accumulate facts and to base 

 on these his own hypothesis rather than, starting with 

 a ready-made hypothesis, to try and adapt his facts 

 to it. With this caution we think these lectures 

 should serve as a stimulant to the jaded investigator 

 depressed by the slowness of his own advance, as he 

 perhaps remembers that it took Ross some two years 

 or so to work out the mosquito cycle of the malaria 

 parasite, and that the first hypothesis as to the path 

 followed by the parasite in the mosquito was a wrong 

 one. 



While, then, a perusal of these lectures has raised 

 some doubts in our minds as to the general validity 

 of presenting those, presumably novices, with a 

 number of interesting suggestions, yet for even the 

 veteran there is abundance of sound common sense 

 to be found here which he will do well to treasure up. 

 If, further, we venture to criticise various statements 

 in detail, we do not do so in a spirit of opposition, but 

 simplv as an expression of a difference of opinion. 

 The author (p. 2) refers to helminthology as " until 

 recently an insignificant if not a despised branch of 

 pathology"; but surely this is somewhat forgetful 

 of the claims on our gratitude and respect of such 

 helminthologists as Leukart, Dujardin, Rudolphi, 

 Cobbold, Kiichenmeister, &c. We can only in part 

 agree with the opinion that, regarded " as a culti- 

 vating medium, there is no difference between the 

 juices and tissues of an Esquimaux and those of a 

 Caucasian or those of a negro." For what else but 

 a difference of medium is the explanation of the fact 

 that the healthy countryman will survive wounds and 

 infections that prove fatal to the less resistant towns- 

 man? It is partly a difference of medium in the host, 

 wo believe, that causes malaria to be a mild disease in 

 temperate regions, and a deadly one in tropical climates, 

 where in both cases we may be dealing with a single 

 infection of a particular person. In what else does 

 the good of change of air, a sea voyage, &c. , consist, 

 but in producing a change of medium in the host in 

 which, e.g., the dysentery amoeba is living? 



In treating of filariasis (p. 80) we do not think 

 the author sufficiently emphasises the fact that the 

 final link in the chain of evidence connecting the 

 mosquito with the transmission of filaria is wanting. 

 Grassi and Noe's experiments on the transmission of 

 filariae to dogs bv means of mosquitoes are by no 

 means convincing, and to experiment on man is 

 hardly possible. In the case of the malaria parasite 

 the experiment has been done several times, but it 

 was Schaudinn who actually first saw the malarial 

 sporozoit penetrate the red cell. We had made the 

 same experiment as Schaudinn on many occasions 

 without success, except that we saw the sporozoit 

 transformed into a body indistinguishable from a so- 

 called " ring form," and if the investigator follows 

 out the method given on p. 98 he will not see what 

 Schaudinn describes. For Schaudinn expressly says 

 that on using sporozoits taken from the salivary 

 gland he got no results ; it was only on using sporo- 



