lO 



NATURE 



['November i, 1900 



particular organism may under different conditions as- 

 sume changes in shape, and that even under apparently 

 the same conditions variations in shape and size may 

 occur. 



The organisms of a spherical shape are termed Cocci, 

 the individual cells appearing as spheres, except during 

 the period of fission, when elongated or lance-shaped 

 forms occur — e.g. Diplococcus pneutnomae. The mode 

 of cell-division determmes the nomenclature applied to 

 the various classes of cocci — those dividing in one 

 direction and remaining attached in pairs or chains are 

 termed diplo- or strepto-cocci ; those dividing in two 

 directions and forming groups of four — tetracocci ; those 

 dividing in three directions and forming packets — 

 sarcinae ; and those dividing irregularly into grape-like 

 clusters — staphylococci. 



The standard of measurement for bacteria is the 

 mikron, equal to i/iooo part of a millimetre, and repre- 

 sented by the sign /i. The diameter of the cocci varies 

 from about o"3 to 3/x. 



The organisms in which the length is always greater 

 than the breadth are termed bacilli. Their shape is 

 cylindrical, and they assume a rod-like form ; of the most 

 important forms the length may vary from o'5/i to ysix, 

 and the breadth from 05 to o'8^. The bacilli may occur 

 isolated, in pairs, or in chains. 



The third main group, the spirilla, are spiral in shape, 

 or more accurately their form represents the fraction of 

 the thread of a screw. The spirilla, like the bacilli, divide 

 in one direction, and may occur as comma, S-shaped or 

 corkscrew forms. The cholera organism has a diameter 

 of about o'4/:i. 



The transverse diameter is usually taken as the standard 

 of measurement, as it is more constant than the long 

 diameter of the bacteria. 



The dimensions of the organisms shown in the accom- 

 panying illustrations are as follows : — Streptococcus 

 pyogenes, o'6-o'8/it ; Staphylococcus pyogenes aureus, 

 07-1/1 ; Diplococcus pneumoniae, o"5-o*8/x ; Bacillus 

 pestis, B. o*6/x, L. o'6 - 1 '9/1 ; Spirillum chnlerae, 

 B. o'4-o*6^, L. o"8-2^ ; Bacillus typhosus, B. o-6-o"8/x, 

 L. i-3'2/Li; Bacillus tetani, B. o'5/i, L. i'2-3'6/i. 



The example seen in Fig. i is the Streptococcus pyogenes, 

 which is responsible for various septic processes in man. 

 The grouping into chains is a characteristic feature of 

 this organism. There is little variation in size of the in- 

 dividual members of the chain, with the exception of 

 detached or isolated cells, which may be double the size 

 of the normal cocci, e.g. when cell-division occurs. .Micro- 

 cocci are not generally subject to such individual varia- 

 tions as bacilli, as can be seen in Fig. 2, Staphylococcus 

 pyogenes aureus, where only slight variations in size are 

 to be detected. In Fig. 3 is an example of a very pleo- 

 morphic organism, the plague bacillus. It is ordinarily 

 a very short, thick rod, almost appearing as a diplococcus 

 when subdivision occurs. In the photograph, one rod is 

 seen which is about six times the size of the others, and 

 this is by no means uncommon. In a fluid culture the 

 form of the plague bacillus is entirely altered, the organism 

 almost assuming the appearance of Fig. i. The Micro- 

 coccus pneumoniae (Fig. 4) is one of the most variable of 

 the diplococci, the individuals in a pair being rarely 

 equal in size, and sometimes elongated, as seen in the 

 photograph. The cholera organism (Fig. 5) is inconstant 

 in size, and its chief characteristic is the bent rod or 

 comma shape. The tetanus bacillus (Fig. 6) is of large 

 size in relation to the other organisms noticed. It is 

 usually a straight rod, except when spore-formation 

 occurs, when it assumes the drum-stick appearance, as 

 seen in the photograph. The typhoid bacillus (Figs. 7 

 and 8) is very variable in size, although its rod-like shape 

 is constant. The organisms generally have been stained 

 with gentian violet, except in Fig. 8, where Van 

 Ermengem's method for demonstrating flagella has 



NO. 16 18, VOL. 63] 



is not a true 

 a deposit of a 



been adopted. This process 

 staining method, it is really 



silver-salt on the organism and its flagella. The 

 organism appears much larger than when stained in the 

 ordinary way. Many organisms are like the typhoid 

 bacillus, endowed with flagella, which are probably 

 exclusively organs of locomotion. In Fig. 8 they sur- 

 round the bacillus, and are many times longer than 

 the organism itself In other organisms one finds some- 

 times unipolar or bi-polar flagella. 



The illustrations accompanying this article have been 

 produced in the photographic laboratory of the Jenner 

 Institute of Preventive Medicine. The magnification is 

 in all cases 1750 diameters, this being regarded as the 

 highest at which satisfactory photographs of bacteria 

 can be taken, a higher magnification generally resulting 

 in the outline of the organism becoming blurred. The 

 objectives used were a Zeiss 3 mm. apochromatic and 

 a Winkel r8 mm. fluorite system, low-power projection 

 oculars being used in each case, and magnification ob- 

 tained by suitable camera extension. The organisms 

 were all stained, so that a yellow screen was necessary 

 when photographing. The screen used was a saturated 

 solution of acridine yellow, about 15 mm. thick, and with 

 this uniformly satisfactory results have been obtained. 



Allan Macfadyen. 

 J. E. Barnard. 



NOTES. 



The loist anniversary of the death of Domenico Cirillo, 

 friend of Linnaeus, and famous both as botanist and physician, 

 occurred on Monday, October 29. . The account of the life and 

 work of this great Neapolitan, given by Prof. Giglioli in another 

 part of the present issue, appears, therefore, at a very appro- 

 priate time, and will be read with much interest by every 

 naturalist. We are glad to be able to publish this appreciative 

 notice of some of Cirillo's contributions to science, and thus to 

 add to the number of those who, knowing his works and career, 

 will cherish his memory. 



The announcement of the death of Prof. Max Miiller, at 

 Oxford on Sunday last, has been received with universal regret. 

 The funeral has been arranged to take place to-day at Holywell 

 Cemetery, Oxford. 



According to a Times report from Constantinople, "An 

 Imperial Trade prohibits star- worship and Sabianism in Turkey." 

 It would be interesting to know more exactly what has been 

 prohibited. 



The new science laboratories at King's College were opened 

 by Lord Lister on Tuesday afternoon. 



The death is announced of Mr, William Anderson, professor 

 of anatomy to the Royal Academy of Arts, and the author of a 

 number of works on surgery and anatomy. 



A COURSE of Cantor lectures by Prof. J. A. Fleming, F.R.S., 

 on "Electric Oscillations and Electric Waves," will be 

 delivered on Monday evenings in November and December at 

 the Society of Arts. 



A DESTRUCTIVE scries ot earthquake shocks occurred at 

 Caracas, the capital of Venezuela, and the surrounding districts 

 on Tuesday, October 30. The town of Guaronas has been 

 entirely destroyed. 



A VISIT to the Chelsea Physic Garden is enough to convince 

 any one of the urgent need of new greenhouses to replace the 

 dilapidated structures in which the existing collections are housed. 

 A more ruinous building than the central range it would be 



