PROFESSOR TYNDALL. 131 



tubes, as given by its talented inventor, is embodied in the plate at the end 

 of the Atlas devoted to mechanical appliances. This simply constructed 

 apparatus consists of a square wooden chamber or box, having a glass 

 front, side windows, and back-door. Through the bottom of the chamber 

 test-tubes pass, packed air-tight, with their open ends protruding for about 

 one-fifth of their length into the chamber. Provision is made through 

 sinuous glass tubings for the free access of air from without, but through 

 which, on account of their sinuous form, no germinal or other dust obtains 

 admission to the central chamber. The top of the chamber is perforated 

 by a circular hole two inches in diameter, and closed air-tight by a sheet 

 of indiarubber. This is pierced in the middle by a pin, and through the 

 pin-hole is pushed the shank of a long pipette, ending above in a small 

 funnel. The shank also passes through a stuffing-box of cotton-wool, 

 moistened with glycerine ; so that, tightly clasped by the rubber and wool, 

 the pipette is not likely in its motions up and down to carry any dust 

 into the chamber. The four legs upon which the chamber is elevated are 

 of sufficient height to permit of the application of a spirit-lamp, or other 

 heat-generator, to the bases of the depending test-tubes. 



Proceeding now to an examination of the more important data bearing 

 upon the subject of spontaneous generation, obtained through the investiga- 

 tions of Messrs. Dallinger and Drysdale, it must be mentioned, in the first 

 place, that the evidence elicited through their researches was arrived at from 

 an entirely diffisrent standpoint, and, in the second place, that it fills up an 

 important hiatus held by the heterogenists to be present in the chain of 

 evidence adduced by Professor Tyndall. Notwithstanding that the only 

 reasonable and inevitable inference to be drawn from the results of his 

 experiments was that infusorial germs of exceeding minuteness were ever 

 present in the ordinary atmosphere, and ready to germinate in the first 

 suitable fluid medium with which they came in contact, it has been urged 

 by his opponents that there is no direct proof of the actual presence of 

 these countless ultra-microscopic germs, and that his evidence is therefore 

 of an entirely negative character. But, to those who are well versed 

 in the life-phenomena of this special class of organisms, the connection 

 between the impalpable germinal dust gathered by Professor Tyndall from 

 the laboratory floor or revealed by the electric beam, and the crops of 

 animated beings produced out of it when sown in the sterilized fluid, 

 is inductively as certain as that the celestial nebulae, as yet unresolved into 

 their ultimate elements by the telescope, consist of star-aggregations similar 

 to those of the nearer and more familiar constellations. 



Fortunately for the cause of the panspermists, this one weak joint in 

 their armour, if such may be said to have been left open — this one little 

 loophole for doubt, out of which the heterogenists have attempted at the 

 eleventh hour to make good their untenable position — has now to be 

 finally closed up. The propagation of infusorial organisms by germs or 

 spores of ultra-microscopic minuteness, has been definitely and most 



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