June 24, 1922] 



NA TURE 



813 



The kind of statement put forward in order to do 

 honour to Manson, but really of a misleading nature, 

 is exemplified in the following from Dr. Sambon's 

 letter in Nature of May 27. He writes : "Sir 

 Ray Lankester ignores Manson's brilliant interpreta- 

 tion of the ' flagellating ' malarial parasite, looked 

 upon by the Italians as a form of degeneration ; 

 by Manson as the prelude to a further all-important 

 developmental stage outside the body of man." 

 The reader of Dr. Sambon's letter would suppose 

 that INIanson had in this matter had " a happy 

 thought " and had put forward a successful specula- 

 tion. Such is not the case. The nature and signific- 

 ance of the flagelliform bodies developed by the malaria 

 parasite were first discovered by Dr. W. G. MacCallum, 

 of the Johns Hopkins University, Baltimore, and 

 published by him at the meeting of the British 

 Association in Toronto, August 1897, and more 

 fully set forth with admirable illustrations in the 

 journal of Experimental Medicine, vol. iii., 1898. 

 He describes the rapid formation of these bodies 

 in the Halteridium of birds (crows) as others had 

 already done both in that case and in the malarial 

 parasites of man. What is of capital importance in 

 MacCallum's paper is the careful description and 

 drawings of the active — even violent — union of the 

 liberated flagelliform bodies with certain granular 

 spheres or female gametes. A single flagelliform 

 body was thus seen to fuse with one female gamete. 

 MacCallum, having once recognised this sexual process, 

 observed it daily, and then observed the same process 

 in the aestivo-autumnal parasites taken from two 

 cases of malaria in a human subject. 



In discussing the significance of his discovery, 

 MacCallum writes that the whole Italian school 

 believed the flagelliform bodies to be due to degenera- 

 tive changes. "Manson," he writes, "as is well 

 known, has advanced the idea that the flagellate 

 bodies represent the forms in which the parasite 

 exists outside the human body, that the flagella 

 penetrate from the stomach into the body of mos- 

 quitoes which have sucked the blood of infected 

 human beings, and that, after a further unknown 

 process of development, they come again (through 

 the water in which the mosquitoes deposit their eggs 

 and die) into the human body." This and other 

 suppositions were entirely set aside by MacCallum's 

 discovery. MacCallum insists that Manson's idea 

 is not based on any observations, but is pure 

 hypothesis ! Manson's interpretation of the flagel- 

 lating malarial parasite was, though erroneous, 

 a legitimate hypothesis, but it certainly was not 

 " brilliant," although we are asked by Dr. Sambon to 

 regard it as being so. E. Ray Lankester. 



June 5, 1922. 



The Isotopes of Tin. 



The insensitivity of the photographic plate in 

 recording positive rays when compared with its 

 sensitivity to light has long been observed, and has 

 been accounted for by the fact that the action of 

 positive rays is purely a surface effect. There has, 

 therefore, always been the hope that considerable 

 improvement could be made in this direction by 

 increasing the concentration of the bromide particles 

 on the surface of the gelatine. This hope has now 

 been realised to some extent by the use of a method 

 which, I. understand, has been devised for the pro- 

 duction of Schumann plates. It consists essentially 

 in dissolving off more or less of the gelatine by means 

 of acid. I have not yet succeeded in obtaining 

 certain or uniform effects, but in the most favourable 

 cases the sensitivity of the ' Half Tone " plates used 



NO. 2747, VOL. 109] 



in the mass-spectrograph has been increased ten to 

 twenty times without seriously altering their other 

 valuable properties. 



The immediate result has been the definite proof 

 of the complex nature of the element tin which had 

 been previously suspected {Phil. Mag. xlii. p. 141, 

 July 192 1). Tin tetramethide was employed, and 

 a group of eight lines corresponding approximately 

 to atomic weights 116 (c), 117 (f), 118 (b), 119 (e), 

 120 (a), 121 (h), 122 (g), 124 (d) was definitely proved 

 to be due to tin. This conclusion was satisfactorily 

 confirmed by the presence of similar groups corre- 

 sponding to Sn(CH3), Sn(CH3)2 and Sn(CH3)3- The 

 intensities of the various components indicated by 

 the letters in brackets agree quite well with the 

 accepted chemical atomic weight 1187, and incident- 

 ally preclude the possibility that any of the lines, 

 with the possible exception of the extremely faint one 

 at 121, are due to hydrides. 



. The spacing of these eight lines, which are only 

 just resolved, show that their differences are integral 

 to the highest accuracy, but the lines themselves 

 compared with known lines on the plate give atomic 

 weights always tending to be 2 or 3 parts in 1000 

 too light for the above whole numbers. That this 

 remarkable divergence cannot be explained as 

 experimental error is very strongly indicated by the 

 following consideration. The discharge tube had 

 been used previously to investigate some very pure 

 xenon. The line due to Sn"o (CH3) should therefore 

 have appeared exactly halfway between the two 

 strong xenon lines 134, 136. It was actually quite 

 unmistakably nearer the former, so much so that 

 the two were only partially resolved. The same 

 irregular grouping repeated itself in another portion 

 of the field in the following spectrum. It seems, 

 therefore, difficult to resist the conclusion that the 

 isotopes of tin have atomic weights which are less 

 than whole numbers by one-fifth to one-third of a 

 unit of atomic weight, but satisfactory settlement of 

 this important point will probably have to be deferred 

 till a more accurate mass-spectrograph has been made. 



Incidentally I may add that the presence of the 

 two faint components of xenon 128 and 130 previously 

 suspected has now been satisfactorily confirmed. 



F. W. Aston. 



Cavendish Laboratory, Cambridge, June 7. 



The Spiracular Muscles of Hymenoptera Aculeata. 



I DESIRE to direct the attention of entomologists to 

 a recently discovered muscle (see Bee World, vol. iii. 

 p. 282, April 1922) present in the honey bee [Apis 

 mellifica), and probably in many others of the 

 Hymenoptera Aculeata. 



The abdominal (respiratory) muscles of Apis 

 mellifica were described by Carlet {Comptes rendus, 

 Acad. Sci., Paris, 1884, vol. 98, p. 758)- His list is 

 incorrect ; it misplaces the posterior attachment of 

 the internal oblique muscle and omits the interdorsals 

 and the spiracular muscles. To the latter it is 

 desired to direct attention here. They run from the 

 lateral sternal apophysis to the larger of the two cones 

 of the spiracle on the tergum of the same segment. 

 Thus, when the abdomen is expanded, this muscle is 

 under tension, and will pull open the closing apparatus 

 of the spiracle. During expiration, the abdomen is 

 contracted ; the spiracular muscles will therefore be 

 slack during this process, and it appears highly im- 

 probable that the spiracles actuated by them can 

 open during expiration. The expired air must 

 therefore pass out of the system mainly through the 

 thoracic spiracles ; a fact which renders comprehensible 



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