Feb. 3, 1876J 



NATURE 



269 



his experiments were conducted. But he did find cases 

 of fertilisation after prolonged exposure to the boiling 

 temperature ; and this caused him to come to the con- 

 clusion that under certain rare conditions spontaneous 

 generation may occur. He also found that an alkalised 

 hay-infusion was so difficult to sterilise that it was capable 

 of withstanding the boiling temperature for hours without 

 losing its power of generating life. The most careful ex- 

 periments have been made with this infusion. Dr. 

 Roberts is certainly correct in assigning to it superior 

 nutritive power. But in the present inquiry five minutes 

 boiling sufficed to completely sterilise the infusion. 



Summing up this portion of his inquiry, the author 



marks that he will hardly be charged with any desire to 

 -init the power and potency of matter. But holding the 

 notions he does upon this point, it is all the more incum- 

 bent on him to affirm that as far as inquiry has hitherto 

 penetrated, life has never been proved to appear inde- 

 pendently of antecedent life. 



Though the author had no reason to doubt the general 

 iftusion of germs in the atmosphere, he thought it desi- 

 rable to place the point beyond question. At Down, Mr. 

 Darwin, Mr. Francis Darwin ; at High Elms, Sir John 

 Lubbock ; at Sherwood, near Tunbridge Wells, Mr. 

 Siemens ; at Pembroke Lodge, Richmond Park, Mr. 

 RoUo Russell ; at Heathfield Park, Messrs. Hamilton ; 

 at Greenwich Hospital, Mr. Hirst ; at Kew, Dr. Hooker ; 

 and at the Crystal Palace, Mr. Price, kindly took charge 

 of infusions, every one of which became charged with 

 organisms. To obtcin more definite insight regarding 

 the diffiision of atmospheric germs, a square wooden tray 

 was pierced with 100 holes, into each of which was dropped 

 a short test-tube. On Oct 23, thirty of these tubes were 

 filled with an infusion of hay, thirty-five with an infusion 

 of turnip, and thirty-five with an infusion of beef. The 

 tubes, with their infusions, had been previously boiled, 

 ten at a time, in an oil-bath. One hundred circles were 

 marked on paper so as to form a map of the tray, and 

 every day the state of each tube was registered upon the 

 corresponding circle. In the following description the 

 term " cloudy '' is used to denote the first stage of tur- 

 bidity ; distinct but not strong. The term " muddy " is 

 used to denote thick turbidity. 



One tube of the 100 was first singled out and rendered 

 muddy. It belonged to the beef group, and it was a 

 whole day in advance of all the other tulses. The pro- 

 oTcss of putrefaction was first registered on Oct 26 ; the 



nap " then taken may be thus described :— 



Hay. — Of the thirty specimens exposed one had be- 

 come " muddy "—the seventh in the middle row reckon- 

 ing from the side of the tray nearest the stove. Six tubes 

 remained perfectly clear between this muddy one and the 

 stove, proving that differences of warmth may be over- 

 ridden by other causes. Every one of the other tubes 

 containing the hay infusion showed spots of mould upon 

 the clear liquid. 



Turnip. — Four of the thirty-five tubes were vefy 

 muddy, two of them being in the row next the stove, one 

 four rows distant, and the remaining one seven rows 

 away. Besides these six tubes had become clouded. 

 There was no mould on any of the tubes. 



Beef.— OnQ tube of the thirty-five was quite muddy, in 

 the seventh row from the stove. There were three cloudy 

 tubes, while seven of them bore spots of mould. 



As a general rule organic infusions exposed to the air 

 during the autumn remained for two days or more per- 

 fectly clear. Doubtless from the first germs fell into 

 them, but they required time to be hatched. This period 

 of clearness may be called the " period of latency," and 

 indeed it exactly corresponds with what is understood by 

 this term in medicine. Towards the end of the period of 

 latency, the fall into a state of disease is comparatively 

 sudden ; the infusion passing from perfect clearness to 

 cloudiness more or less dense in a few hours. 



Thus the tube placed in Mr. Darwin's possession was 

 clear at 8.30 A.M. on Oct 19, and cloudy at 4.30 p.m. 

 Seven hours, moreover, after the first record of our tray 

 of tubes, a marked change had occurred. It may be thus 

 described : — Instead of one, eight of the tubes containing 

 hay-infusion had fallen into uniform muddiness. Twenty 

 of these had produced Bacterial slime, which had fallen 

 to the bottom, every tube containing the slime being 

 covered by mould. Three tubes only remained clear, but 

 with mould upon their surfaces. The muddy turnip- 

 tubes had increased from four to ten ; seven tubes were 

 clouded, while eighteen of them remained clear, with here 

 and there a speck of mould on the surface. Of the beef, 

 six were cloudy and one thickly muddy, while spots of 

 mould had formed on the majority of the remaining tubes. 

 Fifteen hours subsequent to this observation, viz. on the 

 morning of Oct. 27, all the tubes containing hay-infusion 

 were smitten, though in different degrees, some of them 

 being much more turbid than others. Of the turnip- 

 tubes, three only remained unsmitten, and two of these 

 had mould upon their surfaces. Only one of the thirty- 

 five beef-infusions remained intact A change of occu- 

 pancy, moreover, had occurred in the tube which first 

 gave way. Its muddiness remained grey for a day and a 

 half, then it changed to bright yellow green, and it main- 

 tained this colour to the end. On the 27th every tube of 

 the hundred was smitten, the majority with uniform tur- 

 bidity ; some, however, with mould above and slime 

 below, the intermediate liquid being tolerably clear. The 

 whole process bore a striking resemblance to the propa- 

 gation of a plague among a population, the attacks being 

 successive and of different degrees of virulence. 



From the irregular manner in which the tubes are 

 attacked, we may infer that, as regards quantity, the 

 distribution of the germs in the air is not uniform. The 

 singling out, moreover, of one tube of the hundred by 

 the particular Bacteria that develop a green pigment, 

 shows that, as regards quality, the distribution is not 

 uniform. The same absence of uniformity was manifested 

 in the struggle for existence between the Bacteria and the 

 penicillium. In some tubes the former were triumphant ; 

 in other tubes of the same infusion the latter was trium- 

 phant. It would seem also as if a want of uniformity as 

 regards vital vigour prevailed. With the self-same infu- 

 sion the motions of the Bacteria in some tubes were 

 exceedingly languid, while in other tubes the motions 

 resembled a rain of projectiles, being so rapid and violent 

 as to be followed with difficulty by the eye. Reflecting 

 on the whole of this, the author concludes that the germs 

 float through the atmosphere in groups or clouds, vnlh. 

 spaces more sparsely filled between them. The touching 

 of a nutritive fluid by a Bacterial cloud w'ould naturally 

 have a different effect from the touching of it by the inter- 

 space between two clouds. But as in the case of a 

 mottled sk)', the various portions of the landscape are 

 successively visited by shade, so, in the long run, are the 

 various tubes of our tray touched by the Bacterial clouds, 

 the final fertilisation or infection of them all being the 

 consequence. The author connects these results with the 

 experiments of Pasteur on the non-continuity of the cause 

 of so-called spontaneous generation, and with other 

 experiments of his own.* 



On the 9th of November a second tray containing one 

 hundred tubes filled with an infusion of mutton was ex- 

 posed to the air. On the morning of the i ith six of the 



• In hospital practice the opening of a wound during; the passage of a 

 Bacterial cloud would have an effect very different from the opening of it 

 in the interspace between two clouds. Certain caprices in the beha\iour of 

 dressed wounds may possibly be accounted for in this way. Under the 

 heading " Nothing new under the Sun," Prof. Huxley has just sent me the 

 following remarkable extract: — "Ucbrigefts Kann man sich die in der 

 Atmosphare schwimmenden Thierchen wie Wolken denken, mit denen ganz 

 leere Luftmassen, ja ganze Tage vollig reinen Luftrerhaltnisse wcchseln." 

 (Ehrenberg, "Infusions Thierchen," 1838, p. 525.) The coincidence of 

 phraseology is surprising, for I knew nothing of Ehrenberg's conception. 

 My " clouds," however, are but small miniatures of his. 



