318 SCIE
III these days or renewed interest in the cstabliBhment of phyaical laboratories, it is in- teresting to read Maxwell's views of the beat 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 proteuorehip: one wonts popular lectures, and tlie other cares more for experimental work. I think there should bo a BraiUtion, — popular lectures and rough experiments for the masseii, real experiments for real iCudenls, anil laborious eiperlmenta for Bra^rate men."
Rarely has the true solution of the pi-oblem of the proper course in the direction of a lab- oratory been more clearly stated.
Many who know nothing of the nature of the studicB to which Maxwell devoted his life, will read his life, and find it a fascinating one. The pliilosopfaer will ponder over the views of the structure of the universe, and Maxwell's endeavor to do his duty in a world some of whoso mysteries he set himself to discover. The phj-aicist 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 j>oint 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 saliefying thing in the end.
��LiKB most other new doctrines, the cellular theory has been given too wide an interpreta- tion. Within the last few years, 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 oi^ans. 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
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��NCE. tVoL. v.. No. 115.
regeneration of injured tissues, it is certainly true, even in its most extreme form. At thia 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 Carnoy.
Robert llooke (1605) 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 tbem 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 (1680-9.5), 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 Hquid.
The next advance was made in 1781^ when Fontana described and figured within aome cells an ' oviform body proiided in the centre with a siKit.' This earliest observation of the cell-nuoleus remained practically unheeded for flfly 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 nudeolua, was redis- covered by Valentin in 183G. At thia 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, chlorophyl bodies, and crystals had also been seen in various cells.
The next step forward was the recognition of cells as independent individuala, or ' ele- mentary organisms.' Turpin and Mirbel pro- mulgated this view about 182<! ; but it wu Sehleiden's ' Gnindziige der wiss^nschaftlichen botanik' (1842) that led to any general ac- ceptance of it by scientific men. Since then, Schwann, Max Hchultze, Briicke, and many others, have firmly established it.
Meanwhile, the relation of cells to the lai^ 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 otbeR) especially Hugo von MoliI (1S27), finally de- monstrated that vegetable tissues, ns a whole, were but aggregates of more or less modifled cells, which had a common origin, and were all at first alike, but often became greatly altered in the growth and development of ..t'
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