318 



SCIENCE. 



[Yol. V., No. 115. 



In these days of renewed interest in the 

 establishment of physical laboratories, it is in- 

 teresting to read Maxwell's views of the best 

 method of conducting these laboratories. In 

 a letter to Mrs. Maxwell, he says in regard to 

 the Cavendish laboratory at Cambridge, — 



" There are two parties about the prof essorship : 

 one wants popular lectures, and the other cares more 

 for experimental work. I think there should be a 

 gradation, — popular lectures and rough experiments 

 for the masses, real experiments for real students, 

 and laborious experiments for first-rate men." 



Rarely has the true solution of the problem 

 of the proper course in the direction of a lab- 

 oratory been more clearly stated. 



Many who know nothing of the nature of 

 the studies to which Maxwell devoted his life, 

 will read his life, and find it a fascinating one. 

 The philosopher will ponder over the views of 

 the structure of the universe, and Maxwell's 

 endeavor to do his duty in a world some of 

 whose mysteries he set himself to discover. 

 The physicist will find it easier to read the 

 treatise on heat, and the treatise on electricity 

 and magnetism, by becoming better acquainted 

 with the habits of thought of Maxwell as they 

 are revealed by his own letters in this little 

 volume. The devout Christian will find in 

 Maxwell an exemplar to whom he can point 

 with unanswerable words as an illustration of 

 the satisfying power of the Christian faith to a 

 mind which has had few equals in the history 

 of the world, and which, nevertheless, clung 

 to the Christian religion as the only satisfying 

 thing in the end. 



THE PART PLAYED BY THE CELL IN 

 LIVING ORGANISMS. 



Like most other new doctrines, the cellular 

 theor} 7 has been given too wide an interpreta- 

 tion. Within the last few } r ears, botanical 

 research has proved that the essential living 

 part, the protoplasm, is often united by slen- 

 der threads passing from cell to cell. A simi- 

 lar connection has also been demonstrated in 

 certain animal organs. Nevertheless, ' cells ' 

 remain actual facts, and very important facts, 

 of which the biologist has to take account. 

 The cellular theory may be modified in detail, 

 but it will remain true in essentials. With 

 regard to certain cells, even in the highest 

 animals, as the amoeba-like corpuscles which 

 creep all over our own bodies in the lymph- 

 channels, and play an important part in the 



La biologie cellulaire : etude comparee de la cellule dans lea 

 deux regnes. Par le Chanoine J. B. Carnoy, professeur a I'uni- 

 versite catholique de Louvain. Lierre, Joseph Van In et cie. 



regeneration of injured tissues, it is certainly 

 true, even in its most extreme form. At this 

 critical epoch in its history, a brief account of 

 the development of the cell-doctrine may be 

 of interest. We condense it from the pages 

 of Canon Carno} 7 . 



Robert Hooke (1665) first applied the word 

 ' cell ' in describing the structure of plants. 

 He did not, however, regard cells as separate 

 pieces of living matter, but compared them to 

 cavities in a continuous mass, like the cells of 

 a honeycomb. Malpighi (1675) recognized 

 that vegetable cells were distinct, apposed, 

 closed sacs. Leeuwenhoek, in his letters to 

 the Royal society of London (1680-95), called 

 especial attention to the cell-membrane or 

 envelope. From this time, for about one 

 hundred years, vegetable cells (animal being 

 unknown) were regarded as little bladders 

 filled with a homogeneous liquid. 



The next advance was made in 1781, when 

 Fontana described and figured within some 

 cells an ' oviform body provided in the centre 

 with a spot. ' This earliest observation of the 

 cell-nucleus remained practically unheeded for 

 fifty years, and then R. Brown of Oxford 

 confirmed and greatly extended it. He first 

 demonstrated that the nucleus was a normal 

 and usual constituent of vegetable cells. The 

 ' spot ' inside the nucleus seen by Fontana, 

 and now known as the nucleolus, was redis- 

 covered by Valentin in 1836. At this epoch, 

 therefore, the cell was defined as " a vesicle 

 with a solid envelope, containing liquid in 

 which a nucleus with its nucleolus floated." 

 Starch grains, chloroplryl bodies, and ciystals 

 had also been seen in various cells. 



The next step forward was the recognition 

 of cells as independent individuals, or ' ele- 

 mentary organisms.' Turpin and Mirbel pro- 

 mulgated this view about 1826 ; but it was 

 Schleiden's ' Grundziige der wissenschaftlichen 

 botanik ' (1842) that led to any general ac- 

 ceptance of it by scientific men. Since then, 

 Schwann, Max Schultze, Briicke, and many 

 others, have firmly established it. 



Meanwhile, the relation of cells to the large 

 plants in which they were found, was being 

 studied. Malpighi and Leeuwenhoek both be- 

 lieved that such plants were essentially made 

 up of juxtaposed cells. Schleiden and others, 

 especially Hugo von Mohl (1827), finally de- 

 monstrated that vegetable tissues, as a whole, 

 were but aggregates of more or less modified 

 cells, which had a common origin, and were 

 all at first alike, but often became greatly 

 altered in the growth and development of the 

 plant. 



