Vol. IV. No. 79. 



THE AGRICULTURAL NEWS. 



12T 



IMMUNITY OF BARBADOS FROM 

 MALARIA. 



An interesting and profit;ible discussion has been 

 taking place in the column.s of the West India Com- 

 mittee Circular on the subject of the distribution of 

 mosquitos, more particuhirly in relation to the 

 absence o{ Anopheles in Barbados. A reference to this 

 fact in a review of Major Hodder's Dextriiction of 

 Mosqititiis, prompted Mr. Gibbons to put forward the 

 suggestion mentioned below. The following is a review 

 of the correspondence b}' the Editor of the Circular: — 



The correspondence which is proceeding in onr columns 

 regarding the destruction of the Anojiheles mosquito, which is 

 admittedly the communicating agent of malaria, and the 

 complete inununity from this pest, which Barbados alone of 

 all the West India Islands api)ears to enjoy, is of more than 

 usual interest to those connected witli the West Indies. 

 Major W. M. Hodder, who was recently engaged in drainage 

 and other works in St. Lucia with the object of stamping out 

 malaria, laid stress on the fact that if the reason why 

 Barbados, although it has swamps and the mosquitos might 

 easily be imported, has no Anopheles and consequently no 

 malaria could be discovered, a much more simple means of 

 destroying the insect would be at hand than by the costly 

 method of drainage and clearing at present employed. 



Jlr. C. Kenrick Gibbons, wlio has resided for many years 

 in Barbados, then propounded the interesting theory that this 

 might be due to the presence in the swamps and jionds of 

 Barbados of a tiny fish which e.\ists in such teeming numbers 

 as to earn the name of ' millions,' whose staple diet is the 

 larvae of mosquitos. 



Major Hoddfer, in an instructive letter, tabulated the 

 sui)posed reasons for the immunity of Barbados, namely, 

 physical and meteorological conditions unfavourable to 

 the Anopheles ; a microbe enemy or poison to which these 

 mosquitos fall victims ; the existence of the voracious 

 'millions;' or the possibility that the Anopheles had never 

 been imported. Of these four suggested reasons only the 

 second and third could be jiut to a practical test, and already 

 Major Hodder had proposed to take water from two or three 

 swami)S in Barbados and watch its effects in .St. Lucia when 

 he was recalled from foreign service. 



No less an authority than Sir Patrick Manson has 

 now contributed his views to the discussion, and in 

 a letter which we give in another column he reminds 

 us that a case of local immuinty from malaria analogous 

 to that of Barbados is found in the Pacific Islands, 

 where elephantiasis and filarial diseases are very prevalent, 



Awhile malaria in many of the islands is unknown. With 

 regard to the Pacific Islands it is possible, of course, 

 that the Anopiheles has never been imported, but this is 

 inconceivable in the case of Barbados, and Sir Patrick ^Man.son 

 admits the possibility of the correctness of Mr. Gibbons' 

 suggestion, though he naturally declines to accept it without 

 further proof. He points out that there is another and an 

 even more imj)ortant point bearing on the relation of the 

 Anopheles to malaria which demands study, and nnght carry 

 with it useful and practical suggestions. This is, that in 

 certain malarial regions, notably in India, Italy, and 

 Mauritius, there exist circumscribed areas in which, although 

 the Anojiheles abound, malaria is absent, and we agree in 

 thinking that every conceivable effort should be made to 

 ascertain the rea.sons for this apparent anomaly. Many 

 ex|ilanations have been put forward, but they are of little 

 value unless substantiated on the spot. 



There is one weak point in Mr. Gibbons' theory 

 that appears to have escaped notice. There are two 

 species of mosquitos quite common in Barbados, 

 namely, Calex futigans and Stegomyia fasciata. 



The question arises, then, as to why these have 

 not been exterminate<l with the A nophele-'i. It is not 

 that the small fish mentioned by Mr. Gibbons do not 

 eat the larvae of one or both of these species, as he 

 himself says that he has seen them doing so. The 

 evidence for the theory as to the extermination of 

 Anopheles is that Mr. Gibbons has seen these fish eat 

 the larvae of either Cule.r or Steyomyia (or both), 

 neither of which is at all approaching extermination; 

 also there seems nothing in the habits of these 

 mosquitos or their larvae which would render them 

 less liable to attack. 



From a later issue of the West India Committee 

 Circuhir wo learn that steps are being taken to put 

 Mr. Gibbons' theoiy to a practical test. Quantities of 

 the fish have been taken to Colon and British Guiana 

 for the purpose. 



SCIENCE NOTE. 



The Trumpet Tree. 



This tree which is quite common throughout the West 

 Indies is known to botanists as Cecropia 2'<'ltata. It belongs 

 to the natural order Urticaceae which contains also the 

 bread-fruit, jack-fruit, the Assam rubber tree (Ficiis elastica), 

 and other useful plants. The genus Cecropia embraces 

 a number of species indigenous to Tropical America and the 

 West Indies. It receives its common name from the fact 

 that pieces of its hollow stem or branches have been used for 

 making musical instruments. While the trumpet tree does 

 not yield timber as do many other trees of this order, it is 

 of use as a shade tree. Its straight, bare trunk, with large 

 and spreading head, renders it particularly suitable for this 

 purpose. In .Jamaica it is very common throughout the 

 island wherever the virgin forest has been cleared for 

 cultivation. As a shade tree it is employed more particularly 

 in the coffee plantations in the central districts. 



The tree has a somewhat striking appearance, growing to 

 a height of upwards of 50 feet. Its trunk is whitish, about 

 1 foot in diameter. The leaves are large and deeply lobed 

 being covered on the under side with a snow-white down. 



The extremely light wood of this tree is used for making 

 rtoats for fishing nets, and also razor strops. 



An interesting feature of the trumpet tree is the curious 

 relationship with ants which, in some countries, inhabit the 

 hollow stems. This is described by Willis in his Flowering 

 Plants ami Ferns as follows : — 



'The hollows are inhabited by fierce ants (Azteca sp.), 

 which rush out if the tree be shaken and attack the intruder. 

 Schimper has made a thorough investigation of this symbiosis 

 (or living together for mutual benefit) of plant and animal. 

 These ants protect the Cecropia from the formidable leaf- 

 cutter ants.' 



A drug is obtained from the trumpet tree. A related 

 species, Cecropia obtusa, has recently been subjected to 

 minute histological and chemical examination by E. Perrot 

 and E. Choay, whose results are summarized in the 

 Pharmaceutical Journal. Chemical examination of the leaves 

 revealed the presence of small C|uantities of an alkaloid 

 known as cecropine. 



