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MICROSCOPE, USES OF THE. 



MICROSCOPE, USES OF THE. 



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cut into very thiii sections with the aid of a sharp saw. These sections 

 should then be pared down to the necessary fineness upon a hone or 

 smooth stone. This may be effected in the following manner : The 

 section, after having been cut off with the saw, requires to be ground 

 thin before it can be subjected to examination. It may perhaps be 

 as mucl\ as the tenth of an inch in thickness when the grinding is 

 commenced, but by rubbing it for a short time upon a smooth stone 

 it may be reduced to the proper degree of tenuity. Stones which are 

 well adapted for this purpose are the ' Charley Forest ' stones, the 

 Turkey stones, or the Water of Ayr stones, about an inch or more in 

 width, and six inches in length. Each of the four sides should be 

 perfectly smooth. Other stones, or even a piece of slate, answer also 

 very well, and maybe procured at much less cost. The stone is wetted 

 with a little water, and the section rubbed up and down with the 

 finger, or with a piece of cork or leather. 



A very good plan also is to imbed the section slightly in a piece 

 of warm gutta percha, which should extend only a very short distance 

 beyond the edges. This is to be rubbed up and down on the wet hone, 

 water being added as required, till the surface is perfectly smooth, 

 when the section is to be taken off, turned round, and ground down 

 on the opposite side until it is sufficiently thin. The section may also 

 be ground down expeditiously by rubbing it between two hones. If 

 very thick, it will be better to reduce it somewhat with the aid of a 

 flat file before commencing the grinding. After being ground to what 

 is conBii lered the proper thinness, the section may be placed in the 

 microscope, when numerous dark lines will be found all over the 

 surfaces* ; these must be removed by polishing. The deepest of the 

 scratches may be obliterated by rubbing the specimen upon a very 

 smooth part of the hone quite dry. 



Teeth require a little more attention than other hard substances. 

 They should be first ground down upon a lapidary's wheel or upon a 

 dentist's emery wheel. Sections can also be readily cut with a diamond 

 saw (an iron-wheel, the edge of which is covered with diamond dust). 



The thin section is now to be soaked for a short time in ether to 

 remove the fatty matter, and then allowed to dry. 



It is to be subjected to examination in the dry way, moistened with 

 water, turpentine, or Canada balsam, and the different appearances in 

 each case should be carefully observed. 



The cartilaginous basis is to be examined also in thin sections, 

 which may be cut either before macerating in acid, or subsequently. 

 A whole tooth placed in moderately strong acid will become soft in 

 four or five days, when thin sections of different parts may readily 

 be cut with a sharp knife. 



The dentinal tubes may be isolated from each other by longer 

 maceration in acid, and afterwards by soaking for a few hours in 

 dilute caustic soda or potash. It is better in this investigation to cut 

 the thin section before maceration in acid, or to macerate the tooth 

 until moderately soft, and then remove a thin section, which is to be 

 further exposed to the action of the strong acid. A mixture of 

 sulphuric and hydrochloric acids has also been recommended. 



The examination of fluids does not require so much art as that of 

 solid matters. Where it is wished to examine the whole of the con- 

 tents of a fluid, all that is necessary is to place a drop upon a glass 

 slide and to cover it with a piece of thin glass. It frequently happens 

 however that it is the matter suspended in a fluid that it is desirable 

 to examine. Under these circumstances the fluid should be placed 

 in an ordinary test-tube, and after allowing the deposit to settle, the 

 supernatant liquor should be poured off, and a drop of the deposit 

 conveyed to the glass-slide. In other cases a pipette may be made use 

 of to draw up the deposit from the bottom of the test-tube or other 

 vessel in which it may be held. In examining water for living 

 animalcules a small muslin-bag or net may be employed, through 

 which the water may be poured, and the contents of the bag placed 

 on the slide. In this way the J)e*midiece and some of the larger forms 

 of Jnfiuoria are best procured for examination. 



When the quantity of deposit is very small, the following plan will 

 be found of practical utility. After allowing the lower part of the 

 fluid which has been standing to flow into the pipette as above 

 described, and removing it in the usual manner, the finger is applied 

 to the orifici', in order to prevent the escape of fluid when the upper 

 orifice is opened by the removal of the finger. The upuer opening 

 is then carefully closed with a piece of cork. Upon now removing the 

 finger from the lower orifice, the fluid will not run out. A glass slide 

 is placed under the pipette, which is allowed to rest upon it for a 

 short time. It may be suspended with a piece of string, or supported 

 by a small retort-stand. Any traces of deposit will subside to the 

 lower part of the fluid, and must of necessity be collected in a small 

 drop upon the glass slide, which may be removed and examined in the 

 u-iial way. 



Another plan is to place the fluid with the deposit removed by the 

 pipette in a narrow tube, closed at one end, the bore of which is rather 

 leu than a quarter of an inch in diameter. This may be inverted on 

 a glass slide, and kept in this position with a broad elastic India- 

 rubber band. The deposit, with a drop or two of fluid, will fall upon 

 the slide, but the escape of a further quantity is prevented by the 

 nature of the arrangement. 



Amongst the fluids of the human body which may with advantage 

 bo submitted to examination with the microscope, there is none of 



more importance than the urine. This fluid being the great means 

 which nature employs to rid the system of the used-up and effete 

 matter of the body, becomes an index by which the completeness, 

 redundacy, or inefficiency of this function may be examined. The 

 following hints for the examination of this fluid will be found useful. 



The urine which is to be examined should be collected in sufficient 

 quantity, in order to obtain sufficient of the deposit for examination. 



In all cases the urine should, if possible, be examined within a few 

 hours after its secretion, and, in many instances, it is important 

 to institute a second examination after it has been allowed to stand 

 for 24 hours. Some specimens of urine pass into decomposition 

 within a very short time after they have escaped from the bladder ; or 

 the urine may even be drawn from the bladder actually decomposed. 



In other instances, the urine does not appear to undergo decompo- 

 sition for a considerable period, and may be found clear, and without 

 any deposit a day or two, or even longer, after it has been passed. 



In those cases in which lithic acid or oxalate of lime are present, 

 we shall find that the deposit increases in quantity after the urine has 

 stood some time. The latter salt is frequently not discoverable in 

 urine immediately after it is passed, but makes its appearance in the 

 course of a few hours ; depending upon a kind of acid fermentation, 

 which has been the subject of some beautiful investigations by 

 Scherer. 



In order to obtain sufficient of the deposit from a specimen of urine 

 for microscopical examination, we must place a certain quantity of the 

 fluid in a conical glass, in which it must be permitted to remain for a 

 sufficient time to allow the deposit to subside into the lower part. 



Urinary deposits often require to be examined with different 

 magnifying powers, those which are most frequently used being the 

 inch and the quarter of an inch. Large crystals of lithic acid are 

 often readily distinguished by the former, but crystals of this sub- 

 stance are sometimes so minute that it is absolutely necessary to use 

 high powers. Octohedra of oxalate of lime are frequently found so 

 small that they cannot be seen with any power lower than a quarter ; 

 and, in order to bring out the form of the crystals, higher magnifying 

 powers than this are sometimes necessary. Spermatozoa may be seen 

 with a quarter, but they then appear very minute. In these cases, 

 an eighth of an inch object-glass will be of advantage. The casts of 

 the tubes, epithelium, and the great majority of urinary deposits can, 

 however, be very satisfactorily demonstrated with a quarter of an 

 inch object-glass. 



In the investigation of those deposits which are prone to assume 

 very various and widely-different forms, such as litbic acid, it will 

 sometimes be found necessary to apply some simple chemical tests, 

 before the nature of the substance under examination can be 

 positively ascertained. 



The urine is very liable to the introduction of foreign substances. 

 A paper on this subject by Dr. Beale will be found in the first volume 

 of the ' Quarterly Journal of Microscopical Science.' The following 

 is a list of these substances occasionally found by Dr. Beale : 



Fragments of human hair. 



Cat's hair. 



Hair from blankets. 



Portions of feathers. 



Fibres of worsted of various colours. 



Fibres of cotton of various colours. 



Fibres of flax. 



Potato starch. 



Rice starch. 



Wheat starch, bread-crumbs. 



Fragments of tea-leaves, or separated spiral vessels and cellular 

 tissue. 



Fibres of coniferous or other wood swept off the floor. 



Particles of sand. 



Oily matter in distinct globules arising from the use of an oiled 



catheter, or from the accidental presence of milk or butter. 

 Besides the above, there are many other substances, met with less 

 frequently, as, for instance, fragments of silk, mustard, flour, cheese, 

 small fragments of the skin of potato, or of different kinds of fruit, 

 and many others which will occur to the mind of every one. With 

 the microscopical characters of these bodies the student should be 

 perfectly familiar as soon as possible ; and, as they may be obtained 

 without the slightest difficulty, this is easily effected. 



For the nature of the deposits found in the uriuft see the article 

 URINE. 



The examination of the other fluids of the animal body present 

 little difficulty. Next to the urine the blood is of most importance. 

 In order to examine the blood, a small drop is placed upon a glass 

 slide, and covered with thin glass, which is to be pressed down until 

 a very thin, transparent, and almost colourless stratum only remains. 

 If in this manner the individual globules cannot be seen distinctly, 

 a little syrup or serum must be added ; but it is better to avoid the 

 addition of any fluid, if possible. Upon carefully focussing, the red 

 globules will appear to present a dark centre and light circumference, 

 or the reverse, according as the focus is altered, and here and there a 

 white corpuscle may be observed. [BLOOD.] 



If a little strong syrup be added to a drop of blood, the corpuscle? 

 will be found to have become flatter from exosmosis of a part of tiicir 



