RECENT PROGRESS OF NATURAL SCIENCE. 603 



tween a group of individual men who do not know how to organize 

 their strength, and a strictly-disciplined, well-ordered army suitably- 

 formed and well armed, and which, by the strict subordination of the 

 many wills to the central authority, is always equal to the highest 

 achievements. 



It is true that these scientific researches into biology have left as 

 yet the most important questions unsolved. It is not yet possible to 

 regard all life-processes as simple modifications of the other forces of 

 Nature and to ascertain their mechanical equivalents ; we cannot yet 

 convert absolute heat or light into life ; and, although chemistry is 

 daily doing more and more to bridge over the gaping chasm which 

 once separated the organic and inorganic systems, it has not yet suc- 

 ceeded in finding out the precise matter which exclusively supports 

 the life-process, on which alone the cells subsist. Thus, then, the be- 

 ginning of life is still wrapped in obscurity. 



After referring in this connection to the transmission of epidemics 

 among plants, animals, and man, and to the microscopical labors of 

 Leeuwenhoek, Ehrenberg, Gagniard-Latour, Schwann, and Kiitzing, 

 Prof. Cohn goes on to say that the investigators of the present time, 

 to whom Pasteur has given a powerful impulse, have been the first to 

 establish beyond doubt that without Bacteria no putrefaction, and 

 without yeast-fungi no fermentation takes place; that this decomposi- 

 tion is accomplished only through the sustenance and living activity 

 of those microscopic cells. 



Many a mystery of life will doubtless be unfolded to us if our 

 opticians during the next twenty-five years should manage to raise the 

 power of the microscope in the same projDortion as in the previous 

 quarter of a century, in which it has been at least quadrupled. The 

 best microscope of Schick and Plossl in 1846 did not magnify more 

 than 500 diameters ; the " immersion-lens xv." of Hartnack over 2,000 

 diameters. Still Dr. Cohn does not venture to hope that during the 

 next twenty-five years all the questions of science which are at present 

 being agitated will be solved. As one veil after another is lifted, we 

 find ourselves behind a still thicker one, which conceals from our long- 

 ing eyes the mysterious goddess of whom we are in search. 



Dr. Cohn, in concluding his eloquent address, attempts to point out 

 the characteristics which distinguish the present from the past genera- 

 tion. In the former epoch, students confined their researches to single 

 and carefully-marked-off divisions of Nature, without any regard to the 

 neighboring and closely-allied regions, which must necessarily lead to 

 theone-sided view that these divisions belong to Nature herself. In the 

 present generation, on the other hand, the several physical sciences 

 have entered into the closest organic union. Physics and chemistry, 

 along with mathematical astronomy and geology, have been blended 

 into a new science the history of the development of worlds ; 

 palaeontology, systematic botany, and zoology, have been joined into a 



