SPONTANEOUS GENERATION. 



115 



diately after the publication of Dr. Sanderson's 

 notice Huitzinga ' repeated the turnip and cheese 

 experiments with the same result. After thus 

 verifying Dr. Bastian's conclusions, Huitzinga 

 made a fresh series of trials, in which the method 

 was slightly varied. Instead of a turnip-infusion, 

 he used a mixture of grape-sugar and soluble 

 salts, and at the same time he substituted for the 

 insoluble cheese-dust a small quantity of soluble 

 peptone. He also employed different means for 

 excluding the possibility of atmospheric contami- 

 nation, and closed his flasks by cementing on 

 them small disks of earthenware, instead of seal- 

 ing them by heat. These alterations in the pro- 

 cess made no difference in the result. Bacteria 

 regularly appeared when the ingredients were 

 used in certain definite proportions, which Huit- 

 zinga specified. But he added the very impor- 

 tant observation that he could, by altering the 

 proportions of the solutions, keep his fluids ster- 

 ile, although in other respects treated exactly as 

 before, and he justly relied on this differential 

 process as proving that by his method any pre- 

 viously-existing germs in the liquid were de- 

 stroyed and perfect isolation obtained ; for the 

 altered fluids were found as capable as ever of 

 developing swarms of bacteria if once inoculated, 

 though they remained barren when boiled and 

 protected. More recently Prof. Colin, of Breslau, 

 whose name commands the highest confidence on 

 this class of subjects not less in England than 

 in his own country, has directed his attention 

 minutely, to this specific investigation, and he 

 found 5 that hay-infusions, when acid, became 

 fertile after boiling from periods ranging from 

 fifteen to ninety minutes, while some similar in- 

 fusions in the neutral state were not rendered 

 sterile by boiling for two hours, although he in- 

 clined to account for the result on the hypothesis 

 that the death-point had not been reached at the 

 boiling temperature, a matter which will be dis- 

 cussed further on. 



Such an accumulation of evidence as this 

 would, of course, be overwhelming unless met 

 by something like equivalent evidence on the 

 other side; and before touching on any of the 

 other facts or theories involved in the dispute, it 

 will be well to see what the germ-theorists have 

 to say on the single specific question whether it 

 is possible, under any circumstances, for an or- 

 ganic infusion, with or without particles of solid 

 matter in suspension, to putrefy after having 

 been boiled and protected from contact with any 



1 See Mature, March 20, 18T3. 



2 " Beitrage zur Biologie tier Pflanzen," 1S76, p. 259. 



germs or dust which may be contained in the air. 

 They are not quite agreed as to the answer to be 

 given. None of them deny, and most of them 

 have expressly or implicitly admitted, that a tur- 

 nip and cheese infusion will often produce bac- 

 teria under the specified conditions. Some of 

 them still maintain that life never appears in any 

 infusion so treated from which solid particles are 

 excluded, while others limit their denial to acid 

 infusions, and acknowledge that some neutral or 

 slightly alkaline fluids will putrefy, notwithstand- 

 ing previous boiling and adequate protection. 

 How these various conclusions are interpreted by 

 the different sections of the germ-theory school 

 we shall consider further on. For the present we 

 confine our attention to the simple question of 

 fact. In marshaling the proofs on this side, we 

 must give the first place to Pasteur, not only as 

 due to his distinguished position, but because in 

 order of time he preceded almost all of the mod- 

 ern inquirers, not excepting Bastian. 



Pasteur operated for the most part upon a 

 rather limited selection of fluids. His favorite 

 medium was yeast-water sweetened in a certain 

 definite way, which he used so frequently that it 

 acquired the specific designation of " Pasteur's 

 fluid." Nearly all his other experiments were 

 made with milk, with urine, or with Pasteur's 

 fluid, rendered neutral or faintly alkaline by the 

 addition of carbonate of lime, the fluid in its 

 original state being of an acid character. Urine, 

 also, was of course acid, and milk somewhat al- 

 kaline. Pasteur's method of excluding contami- 

 nation was, in general, by allowing the approach 

 of air only through heated tubes, the more per- 

 fect plan of hermetically sealing having been re- 

 jected by him apparently from considerations of 

 convenience. In some cases, also, he used plugs 

 of cotton-wool or bent tubes for the same pur- 

 pose of excluding air-dust, and he seems to have 

 placed a reliance on these methods to which, in 

 other hands, they have scarcely shown themselves 

 entitled. He boiled his fluids from two to five 

 minutes only, and used an incubating tempera- 

 ture of from 25° to 30° C. (77° to 86° Fahr.). 

 The details of his principal investigation are 

 given in the " Annales de Chimie," third series, 

 volume lxiv., published in the year 1862. 



The results obtained were that Pasteur's fluid 

 and urine always remained sterile, while milk and 

 the neutralized Pasteur's fluid always putrefied. 

 He reversed these last results by superheating the 

 alkaline fluids up to temperatures of from 100° 

 to 110° C. (105° being the heat ordinarily em- 

 ployed), a circumstance which will deserve much 



