February 15, 191 2] 



NATURE 



529 



beer plant. Though exceedingly 



to botanists, these discussions are 



main theme, and might with advantage have given place 



to a further treatment of definitely established diseases, and 



more unity and balance would thus have been secured. 



In seeking for some convenient classification of various 

 diseases, the natural division into three large groups is 

 adopted : — (i) the vascular diseases ; (2) the parenchyma 

 diseases without hyperplasia ; and (3) cankers, tubercles, 

 and tumours, in which there is a more or less distinct 

 hyperplasia. Under the general considerations involved in 

 a study of these forms of parasitism, such as the methods 

 of infection and progress of the disease, the destruction of 

 tissues and dissolvent action of enzymes, abnormal develop- 

 ment of host tissues, &c., a great number of bacterial 

 diseases are dealt with by way of illustration, but only 

 three specific diseases are fully described as such. These 

 — the wilt of cucurbits, the black-rot of cruciferous plants, 

 and the yellow disease of hyacinths — belong to the vascular 

 group, and are discussed in fullest detail with respect to 

 the specific characters of the organism, the etiology of the 

 disease, the morbid anatomy, geographical distribution, and 

 remedial treatment, including an estimate of financial loss 

 for which they are responsible. The account of the 

 cucurbit wilt represents Dr. Smith's own work, and he has 



interesting and important 1 jhe PROGRESS IN OUR KNOWLEDGE OF 

 re rather foreign to the | jjj£ TRANSMISSION OF SLEEPING 



SICKNESS AND OTHER 

 DISEASES IN AFRICAN 



TRYPANOSOME 



nPHE latest report of the British Sleeping Sickness Com- 

 mission is the outcome of the work of Colonel Sir 

 David Bruce, Captains A. E. Hamerton, H. R. Bateman, 

 F. P. Mackie, and Lady Bruce, the members of the third 

 commission to Uganda during the years 1908-10. It is 

 highly satisfactory to find that, in the volume before us, 

 a distinct advance is recorded in our knowledge relating 

 to important etiological questions connected with the spread 

 of sleeping sickness and of certain animal diseases due to 

 trypanosomes. 



An introduction, illustrated by photographs, describes the 

 chief features and arrangements of the camp at Mpuniu, 

 which was made the headquarters of the commission. The 

 body of the work is divided into ten sections, the more 

 important sections each comprising several groups of ex- 

 periments. In a few cases these subdivisions represent the 

 continuation or elaboration of an experiment previously 

 recorded (in Report No. x.) ; in such, the result obtained 

 from the original experiment is first of all briefly re- 

 capitulated. .\t the end of the volume is a comprehensive 

 analytical index (to both Reports x. and xi.) 

 which will be found very useful. 



The first section (A), which is in many re- 

 spects of the greatest interest, deals with the 

 development of Trypanosoma gambiettse and 

 other trypanosomes in Glossina palpalis, and 

 the question of their transmission by this 

 tsetse-fly. As regards Trypano.:ot}uj gambi' 

 ense, the following important conclusions are 

 reached by the commission. Mechanical trans- 

 mission, that is to say, transmission by means 

 of interrupted feeding, plays a much smaller 

 part, if any, in the spread of the parasites 

 (and consequently of sleeping sickness) than 

 has hitherto been supposed. .After the first 

 few hours, the bite of the fly was found to 

 be non-infectious until at least twenty-eight 

 days had elapsed since the fly fed on the 

 original infected animal.* At the end of this 

 " incubation period " the fly may become in- 

 fective, and may retain its infectivity for at 

 least ninety-six days. This means that the 

 developmental cycle of the parasites in the 

 insectan host was found to take about twenty- 

 eight days, and only when this development 

 was completed could the infection be trans- 

 mitted back again to the vertebrate host. 

 Once a fly becomes infective, it appears only 

 too likely that it mav remain infective for the 

 rest of its life. On the other hand, agamst 

 this alarming result may be set the fact that 

 only a small proportion of flies (laboratory 

 nih B.tracheifihilushy Diairotica vittatan\^\\\.oi'\\x%\if.\iT, brej) appear to become infective, the com- 



"u°'?\Jlf\"' *"'* "^'"'"^ '" °'^"^' ^ "^'"'''' infection. ,„i^g<o,/ [saving found that the trypanosomes 



^^^^^^^ ^^^^ .^^ ^^^^^ ^ .^^ ^^ ^j ^^^1^ ^. 



fed on an infected animal; and the proportion of 



to non-infective flies occurring wild \\\ nature 



much less, probablv not more than i in 500. 



account is given of the various d. v.-l..p- 



mental phases of the parasites observed in the difi-.nf 



organs of the flv. Stress is laid by the comml^.lon 



upon one fact, namely, that in the salivary glands, 



and in them alone, were the trypanosomes found to 



revert to the blood-type. Further, the occurrence of this 



P"iG. 2. — Wilt of cucurbits. 



Cucumber-plant infected with a pure culture of B. tracheiphilus plated from the stem of a 

 squash-plant. Plant inoculated August lo, 1905, by needle-pricks on blade of leaf 

 marked X. Photograph made on August 22. The vessels of the stem were plugged 

 with a sticky white bacillus, which was plated out. Surface of stem sound. About one- 

 sixth natural size. 



Cucumber-leaf inoculated w 

 1905. Blade shrivelled in 

 Photographed August 26, about half-size, 



also carried out much original research upon the other 

 special diseases enumerated. The three are placed each in 

 separate chapters, and together occupy more than one-third 

 of the whole volume. Perhaps we may look forward at 

 some future date to a third volume dealing more com- 

 pletely with other important types. 



The most notable recent work on bacterial disease is that 

 by Dr. Smith upon the crown gall, and a very interesting 

 epitome of his latest paper is included here. This brilliant 

 piece of investigation has established beyond all question 

 that the tumerous disease known as the crown gall (Fig. i) 

 is of bacterial origin, and the phenomena in connection 

 with this type of bacterial disease appear, in the author's 

 own words, " to throw a flood of light on the mechanism 

 of the development of malignant animal tumours." 



The book is fully illustrated by expressive drawings and 

 photographs, made chiefly from material in the author s 

 own laboratory. Two of the illustrations are here repro- 

 duced. M. C. P. 



on 



infective 

 is very 

 .An interesting 



type" of'^the" parasites' in the salivary glands w^s found to 

 coincide, broadly speaking, with the onset of V^;^^;^ 

 infectivity of the flv. The commission consider that u. !.- 

 out this invasion of the glands there can be "« 'n«;^'-t'^^'>; 

 and that the reversion of the parasites to the blood-type it 

 1 Report, of the Stuping Sickne.. Commi«ion of the Royal Society. 



t^:S:^^^l&<^^^^^ in ,". surrounding conditio^,, (bod. &c 



NO. 2207, VOL. 88] 



