151 



AN I.Ml'KOVIOM Minilon K<»K Ki:< ; ILATI \( ! 'I'lll': 'I'llICKNKSS OF 

 MIC'KOTO.MK SKCrio.NS. 



1'. .M. Am)i:i:\vs. liidiiiiui riiivorsity. 



Ill soiUL' of lli(- .MiiKil' lorius of iiiicidloiiii's si'vi-ral sin-iii^s aiul oilier parts 

 arc arraugiMl in such a uiaiiiicr as to cause" the syocimeu in the luachiiu! 

 to he set out tiic desired distance for sectioniiiK. The ahove iiieiitionod 

 ai-ran-cineni is usually very coin|ilicated. and apparently unnecessarily so, 

 in nian.N machines of lliis l.\i>e. This adds tii'catly to the e\i>eiise. lial)ility 

 to .net out of order, and makes the ai>paratus unduly lariic and heavy. A 

 microtome, as most other types of machines, should not he made heavy 

 simply to remain in one position, hut should only be heavy or suhstantial 

 enoiifih to prevent sprinsinf? or fiettinj; out of allij,'nnient when in use. < »f 

 course this is a point tliat merits due coiisi(lerati(tn in a inicrotonie when 

 such very thin sections are to he out. hut still the present weiglit of most 

 such machines of the microtome type can he greatly reduced without 

 detriment. A simple table clamp is all that is necessary to obviate most 

 of the difficulty of shifting of the position of thu machine. The chief 

 weight is. of course, in the framework of the machine especially in the 

 wheel base, slide pillar and uprights of the microtome I used. This is 

 true of most machines of this typ(>. The weight of these parts could be 

 reduc(>d to one-third or even one-half of what it is without sacrificing any 

 necessary rigidity. The weight of the wheel and frame running on the 

 slide pillar could he much reduced especially by the proper adjustment of 

 the balancing of the weight of the two since they are connected to the same 

 shaft. This same balancing of weight is seen in the adjustment of the 

 pitman rod on the crank of engines and other much more delicate machin- 

 eiy. The difference in weiglits and balancing here refeiTed to in the case 

 of microtomes is so considerable as often to cause considerable inconven- 

 ience and unsteadiness in operating the machine. Part of this adjust- 

 ment, as the machine I used as now arranged, could be partly arranged for 

 by a different length in the threading <if the main shaft so as to throw the 

 heavy parts of the machine, concerned in the motion, more nearly in bal- 

 ance when the microtome is in operation. A macliiue which is arranged for 

 cutting .sections in the ways here described, should be so arranged and ad- 

 justed as to turn or start with equal ease in any position. Its construction 

 should also he such that it could he stopped instantly and at any point 

 without having to turn a special device at the top of the slide pillar. That 

 a microtome is not a machine that is expected to be moved about much, 

 has no bearing <m the question for whether it is moved much or little an 

 unnecessary amount of material and weight is often present in many of 

 its parts which could from the standpoint of cost and convenience often 

 be eliminated. The question of setting the l)lock for cutting tliin sections 

 is arranged in a very accural*' and better way on tlie Jung Sliding Micro- 

 tome by means of an incline plane and a spiral thread of definite value for 

 each adjustment. Even in this machine the weight far exceeds what is nec- 

 essary. The arrangements of springs on the microtome used by me were, 

 as is generally the case soon(>r or later, a source of annoyance and often 



