January 19, 1893] 



NATURE 



28: 



BACILLI IN BUTTER. 



"T^HE fact that milk affords a particularly suitable medium for 

 the growth and multiplication of most micro organisms, 

 has rightly led to its beinij regarded as a dangerous vehicle for 

 the propagation of disease. On the Continent the practice of 

 boiling all milk before use, and so destroying any pathogenic 

 microbes which may be present, is almost universal, and recently 

 a number of special pieces of apparatus have been devised for 

 household use, ensuring the efficient so-called " pasteurization " 

 of milk. In England, however, we but rarely boil our milk in 

 spite of outbreaks of diphtheria and typhoid fever having been 

 not infrequently traced to a particular milk supply. In a paper 

 byCnopfon the bacterial contents of milk it is stated, that on 

 one occasion out of every thirteen samples of milk supplied to 

 Paris one was found to contain tubercle bacilli, whilst it is well 

 known that the germs of typhoid, cholera, diphtheria, anthrax, 

 &c., thrive readily in this medium. But although milk has been 

 made the subject of much careful experimental investigation, 

 comparatively little is known of the microbial condition of butter. 

 Heim has shown that cholera bacilli purposely rubbed into 

 butter could be demonstrated after thirty-two days, whilst 

 typhoid bacilli similarly introduced were found after three weeks, 

 and tubercle bacilli after the lapse of a month, although 

 Gasperini discoveed the latter in butter even after 120 days. 

 Quite recently Lafar has published a paper, "Bacteriologische 

 Studien iiber Butter" in the Archiv fiir Hygiene, in which he 

 has recorded his investigations oti the micro-organisms found in 

 Munich butter. These experiments are instructive as exhibiting 

 the fitness of butter to support a large number of bacteria, and 

 thus furnish an interesting supplement to what is already known 

 concerning the longevity of pathogenic microbes in this medium. 

 The samples examined were prepared from fresh cream and 

 were investigated as soon as possible after the butter was made. 

 It was found that the number of microbes differed according as 

 the portion for experiment was taken from the outside or 

 from the interior of the piece of butter. Thus in one 

 instance whilst one gram from the centre of the pat 

 contained 2,465,555, on the outside in the same quantity as 

 many as 47,250,000 micro-organisms were found. Taking the 

 averageof a number of examinations, it was estimated that the 

 interior of a lump of butter possessed from 10 to 23 millions of 

 bacteria in a single gram. Lafar is inclined to regard this as 

 an under rather than an over-statement of the number, inas- 

 much as there are always probably present a certain proportion 

 of microbes which will not develop at the ordinary temperature, 

 or on the gelatine-peptone medium usually employed. He 

 graphically puts it that, in some cases it is conceivable that the 

 number of organisms swallowed with a moderately-sized slice of 

 bread and butter may exceed that of the whole population of 

 Europe ! Lafar found that butter kept in a refrigerator, with a 

 temperature of between 0° to 4- 1° C. at first (after five days) 

 showed a marked reduction in the number of bacteria, but that 

 no further diminution took place, although the sample was kept 

 for a month at this temperature. Samples kept at from 12° to 

 15' C. exhibited a marked increase in the number of micro- 

 organisms, a rise from 6 to 35 millions being observed in the 

 course of nine days, whilst when placed in the incubator (35" C.) 

 after four days the bacteria had fallen from 25 to 10 millions, 

 and after thirty-four days only 5 per cent, of the original 

 number present were discoverable. Experiments were also 

 made to ascertain what was the bacterial effect of adding salt 

 to butter kept in a refrigerator. It was found that although the 

 numbers were thereby considerably reduced, that yet, even when 

 as much as 10 per cent, of salt was added, the complete 

 destruction ofthe bacteria was not accomplished. On examining, 

 however, gelatine-plates prepared from these samples, it was 

 ascertained that the organisms present consisted almost entirely of 

 a pure cultivation of one particular microbe, which was ap- 

 parently entirely unaffected by the addition of salt, and had 

 grown and multiplied to the exclusion of nearly all the other 

 bacteria originally present. When samples similarly salted were 

 placed in the incubator (35" C.) the result was rather different, 

 for whilst there was more apparent connection between the 

 proportion of salt added and the diminution in the number of 

 bacteria, more varieties of micro-orginism-! were found on the 

 gelatine-plates. But in this case, also, the gevmicidal effect 

 produced was not proportional to the increase in the amount 

 of salt. Samples of artificial butter were also examined, and 

 were invariably foundt o be much poorer in bacteria than ordi- 



nary butter. Thus, whilst the smallest number found in one 

 gram was 747,059, in real butter considerably over two million 

 microbes was the minimum. Two varieties of bacilli have been 

 isolated and described, which were found very constantly 

 present in butter throughout these investigations. They are 

 beautifully illustrated and shown in coloured plates as individual 

 organisms and colonies at the end of the puper. Lafar pur- 

 poses continuing his investigations, and it is to be hoped that 

 the examination of butter for pathogenic micro-organisms, about 

 which so little is known, will form an important feature in any 

 further researches he may undertake. 



Grace C. Frankland. 



THE OCCURRENCE OF NATIVE ZIRCONIA 

 {BADDELEYITE). 



T^HE discovery of native zirconia was first made public in my 

 -*■ letter to Nature (vol. xlvi. p. 620) in October last ; at the 

 same time I gave characters sufficient for the recognition of the 

 new mineral, and suggested the name Baddekyile , in honour of 

 Mr. Joseph Baddeley who had brought the specimen with other 

 dense minerals from Rakwana in Ceylon. As there was only 

 a single fragment of what at first sight seemed a hopelessly im- 

 perfect crystal, the determination of all the important characters 

 without appreciable injury of the specimen was a task of an 

 attractive kind : the technical details of the investigation 

 (including quantitative chemical analyses) and the line of 

 argument by which definite results were evolved from the 

 observations, were communicated to the Mineralogical Society 

 at the meeting held on October 25 (Nature, vol. xlvii. p. 

 70), and crystals of hydrous zirconium oxychloride prepared by 

 identical methods from Baddeleyite and artificial zirconia, 

 respectively, were exhibited for comparison. Having regard 

 to the unexpected result of the chemical examination and the 

 difference of the characters of Baddeleyite from those of arti- 

 ficially prepared crystals of zirconia, every care had been taken 

 to get results as accurate as the material itself would admit of. 



Of course it was hoped that the occurrence of native zirconia, 

 once established, would soon be noticed elsewhere ; and in fact, 

 I hear this morning (January 3) from Dr. Hussak of the Geo- 

 logical Survey of Brazil, that flawless crystals of zirconia are 

 actually met with in the south of Sao Paulo as an accessory 

 constituent of an augitic rock described under the name of 

 Jacupirangite by my friend Mr. O. A. Derby. 



The Brazilian mineral had three or four years ago been 

 regarded by Dr. Hussak (who had then only a small amount of 

 material for examination) as probably orthite (silicate of cerium, 

 iron, &c.), a mineral with which it agrees in its more obvious 

 external characters, and it was mentioned later under that name 

 in Mr. Derby's description of the Jacupirangite ; but more 

 recently Dr. Hussak, on isolating a score of flawless crystals 

 fnmi the decomposed rock, recognized the distinctness of the 

 mineral fro n orthite, determined the geometrical and physical 

 characters of the crystals, and decided from a chemical examina- 

 tion that the material was a tantalo-niobate of probably some 

 member of the yttrium-cerium group : these results were pub- 

 lished in the Neues Jahrbuck fiir Mineralogie, 1892, Band II. 

 p. 142, immediately after my announcement of the occurrence 

 of native zirconia in Ceylon had been sent for publication, but 

 they had been forwarded from Brazil as early as the month of 

 June. Dr. Hussak now informs me that the Brazilian mineral, 

 which had been sent to Sweden for a complete quantitative 

 examination, has been determined by Prof. Blomstrand to be 

 almost pure zirconia. 



As regards crystalline form, the parametral elements obtained 

 by myself for Baddeleyite, and announced at the meeting of 

 October 25, agree in a very satisfactory way with those deter- 

 mined by Dr. Hussak for the Brazilian mineral, while as regards 

 optical characters, the two descriptions are practically identical. 

 The only important deviation of external character is in the 

 specific gravity ; that of Baddeleyite is 6'02S, that of selected 

 crystals of the Brazilian mineral is 5-006. 



Now it. seems almost impossible that the specific gravity of 

 crystals of a simple oxide presenting otherwise identical 

 characters can vary to this extent, and the explanation of all 

 the difficulty will probably be found to be that Dr. Hussak's 

 specimens really belong to two distinct minerals ; that while the 

 crystalline form and optical characters were determined from the 

 one (zirconia), the specific gravity and the chemical composition 



NO. 12 12, VOL. 47j 



