ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 887 



wood of an elm tree, and even the circulation of the blood in the web 

 of a living frog can be exhibited with perfect sharpness of definition 

 up to the very margin of the illuminated field of view. The import- 

 ance of this for scientific lecturing is evident. 



In no department of microscopic work has more ingenuity 

 recently been applied than in the construction of microtomes. These 

 are instruments for cutting numerous very thin sections of substances 

 parallel to one another, either for distribution to large classes or for 

 obtaining successive adjacent portions of a structure, so as to secure 

 an exhaustive examination of it. The somewhat complex instrument 

 devised a couple of years ago by Messrs. Caldwell and Threlfall, of 

 Caius College, Cambridge, and manufactured by the Cambridge Scien- 

 tific Instrument Company, was made to deliver its thin sections in a 

 continuous riband at the rate of 100 per minute, or even twice as 

 many when a water motor was used. They were delivered in conse- 

 cutive order and with the same side upwards. Uniform thinness could 

 also be obtained by an ingenious screw. The great novelty of the 

 instrument consisted in the use of an endless band to receive the sec- 

 tions as they came from the razor. When imbedded in suitable 

 material the sections adhered to one another and came off the razor 

 in a continuous riband. As soon as a sufficient length was cut, the 

 end was picked up by a needle or scalpel and placed on the band, 

 which was adjusted so as to be moved forward, at each throw of the 

 object-carrier, through a distance equal to the breadth of the surface 

 which was being cut. 



Many persons were soon at work to improve and simplify this 

 method and to reduce its cost. This object seems to have been best 

 accomplished by the Cambridge Instrument Company itself. Its 

 improved instrument is called the rocking microtome, a rotary instead 

 of a sliding motion of parts having been employed. Its cost is less 

 than one-sixth of that of the original instrument, and instead of being 

 lifted on to a continuous silk band, the riband of sections falls by its 

 own weight directly from the razor on to a sheet of paper, or on 

 to the glass slide on which the sections are to be finally mounted. 

 Sections as thin as the 1/40,000 of an inch are said to be obtained 

 by this plan. It is much easier to work, is less liable to get out of 

 order, easily packed, and very portable. 



One result of the increased facility of instruction and study 

 in microscopical science appears to bo the rapid multiplication of 

 memoirs and papers dealing v/ith isolated portions of subjects. We 

 do not note in this country that the number of men of real power who 

 devote themselves to these studies and patiently elaborate systems 

 and build up sure edifices of enlightenment increases very greatly. 

 Rather there is a multiplication of men of the second or third rank, 

 who catch the jargon of the reigning school, make respectable re- 

 searches on a few points, and become absorbed in teaching or in other 

 rnoney-carning pursuits. There is a fashion in microscopy as in 

 other things, and it is the fashion to study bacteria and bacilli, just 

 as it formerly was the tiling to pore delightedly over test-slides of 

 diatoms. The bacteria will yiehl a more fruitful harvest, certainly, 



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