122 THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



NABK0WI3TG THE EXPERIMENTAL ISSUE. 1 



EVERY one interested in the subject of spon- 

 taneous generation will remember that 

 Prof. Tyndall made, last year, a series of ingen- 

 ious experiments in which he adopted the meth- 

 od of subsidence for purifying the air to which 

 his putrescible infusions were exposed — that is to 

 say, he placed the infusion in chambers washed 

 on the inside with glycerine, and, before com- 

 mencing the experiment, allowed the air to settle 

 until a beam from the electric lamp revealed no 

 motes in it. By these means all putrefactive 

 germs falling on the bottom and sides of the 

 chamber were caught by the glycerine, and infu- 

 sions of various sorts — animal and vegetable — 

 could be kept in the chamber for any length of 

 time without showing the slightest tendency to 

 putrefy. A similar set of experiments has recent- 

 ly been made by the Rev. W. H. Dallinger, who, 

 operating with the germs of known organisms, 

 has been able to show the rate at which these liv- 

 ing motes fall through the air, and the time after 

 the expiration of which putrescible fluids, in a 

 still atmosphere, are out of danger from their 

 contact. 



When a maceration fluid — such as an infusion 

 of fish in water — is allowed to dry up, it forms a 

 " light, hard, porous, papier-mache-like mass," 

 in which are contained, in incalculable millions, 

 the germs of those organisms to which the putre- 

 faction of the fluid was due. A cake of this sort 

 was taken, derived from a fluid known to contain 

 the germs of two forms of monad, the life-history 

 of which Mr. Dallinger had worked out, name- 

 ly, the " calycine monad " and the " springing 

 rnonad." A small quantity of the powder from 

 this cake was dried at 150° Fahr., a temperature 

 15° above that required to kill the adult form, 

 and was then diffused through the air of a Tyn- 

 dall's chamber. In this chamber were placed 

 vessels containing a putrescible fluid, some open, 

 some covered with lids which could, by a simple 

 mechanical contrivance, be removed without dis- 

 turbing anything else. Twenty-four hours after 

 the exposure of the open basins to the mote-laden 

 atmosphere, the covers of the others were re- 

 moved, and everything was left for a certain time, 

 after which first the open and subsequently the 

 remaining basins were examined. It was then 

 found that in those which had been exposed to 



1 From "Becent Science" in the Nineteenth Century, 

 revised by Prof. Huxley. 



the air from the first the calycine monad occurred 

 in every drop taken from every vessel, and the 

 springing monad in two-thirds of the drops exam- 

 ined. In the vessels which had not been exposed 

 until the air had settled for twenty-four hours, 

 the calycine form was wholly absent in three ves- 

 sels out of four, and in the others occurred only 

 in four drops out of thirty, while the springing 

 form flourished in every vessel. 



The reason of these facts is very curious and 

 very interesting. The calycine monad is a giant 

 of its kind, being about y^ inch in length, while 

 the springing monad is not longer than y^trtt inch. 

 The germs of these naturally bear some propor- 

 tion to the size of their parents, and, consequent- 

 ly, the minute particles of protoplasm which con- 

 stitute the spores of the calycine monad were some 

 ten times as heavy as those of the other, and had 

 nearly all fallen and impregnated the fluid in the 

 open basins before the covered vessels were ex- 

 posed. Mr. Dallinger put the matter to a further 

 test. There is one monad, the " uniflagellate " 

 form, upon which many of his observations had 

 been made ; this in its adult state is about j-^ ~, 

 or jg^ti i ncn m length, and its spores are so small 

 as actually to be invisible with the highest pow r ers 

 of the microscope. Dust from a dried cake con- 

 taining these spores was mixed with some con- 

 taining the comparatively gigantic calycine form, 

 and the former experiment repeated. It was 

 found that nearly all the " calycine " germs had 

 fallen in twenty-four hours, all in forty-two hours, 

 for vessels exposed after the lapse of the last- 

 named time contained not a single calycine monad, 

 while every drop taken from them swarmed with 

 the little uninflagellate form. 



Mr. Dallinger has thus shown most conclusive- 

 ly that whenever a putrid infusion dries up there 

 will be found a powdery mass containing spores 

 which every breath of air will diffuse far and wide, 

 and that some of these spores are so minute as to 

 require two days to fall a few inches in a perfect- 

 ly still atmosphere, so that the distance to which 

 they could be carried, and to which they could 

 spread contagion, is practically unlimited. The 

 bearing of this on the germ-theory is obvious 

 enough. 



Some months since, the spontaneous-genera- 

 tion controversy arrived at an important crisis. 

 Results of the most conflicting character had been 



