184 



THE AMERICAN MONTHLY 



[October, 



be made in any quantity, and kept 

 for any time. The ]:)rocess of 

 mounting is simple. The slide is 

 cleaned, and the flat paper ring 

 placed in the centre ; on this the 

 cover is placed, having the object 

 dried on it, and the two are held 

 together by the forceps and gently 

 warmed ; this serves to attach the 

 ring to the slide and cover, at sev- 

 eral points, so that the forceps may 

 now be laid aside. The next step 

 is to take a glass slip (another slide), 

 and laying this on the cover, to 

 grasp the two slides at each end by 

 the linger and thumb of the two 

 hands, and pressing them tightly 

 together, to warm the slide gently ; 

 by looking at the ring obliquely, on 

 the underside, one can tell at (mce 

 when all the air is pressed out, and 

 the adhesion is complete between 

 the cover and the ring, and also the 

 ring and the slide, and they must 

 be held together a moment or two 

 to cool. If the lac is sufficiently 

 thick on the paper the adhesion 

 takes place quickly, and with mod- 

 erate heat, and there will be no 

 danger of breaking the cover, un- 

 less it has been warped in the pro- 

 cess of warming, which will some- 

 times occur when very thin glass 

 has been heated too much for the 

 purpose of burning off the organic 

 matter, or when the support is too 

 small in diameter, or when it is not 

 flat. I think I may be able to in- 

 duce the leading opticians to manu- 

 facture this paper and also the rings 

 for sale ; for special purposes the 

 paper might be printed beforehand, 

 so that, when mounted, the ring 

 would show on the underside 

 the name of the preparer, or of the 

 object. I cannot conceive of any- 

 thing more satisfactory than these 

 rings. Many large objects which 

 would be crushed if one used only 

 the shellac rings made on the slide, 

 by the use of the turn-table, by the 



giving way of these by softening, 

 and under the necessary pressure for 

 attaching the cover, are perfectly 

 protected by the paper rings. I am 

 satisfled that the balsam mounts 

 will be much less frequently used, 

 as soon as we can And some sure 

 dry process. The diatoms, as a 

 rule, show much better when 

 mounted dry and with whole frus- 

 tules, exhibiting both the side and 

 the front view, also the mode of at- 

 tachment, etc. The dry mounts are 

 certainly to be preferred when they 

 are desired for anything except pret- 

 ty objects, and even for this latter 

 purpose there is often a very great 

 difference in favor of the dry mount. 

 Although I have not used these 

 shellac paper rings for any great 

 length of time, yet I can see no 

 reason why they should not be 

 equal to the simple shellac ring for 

 durability, and very much superior 

 to it in other respects. 



o 



Blood-stains as Evidence in 

 Criminal Cases.* 



BY CHAS. O. CUBTMAN, M. 1). 



The detection of blood-stains on 

 linen or other articles of apparel, 

 has often a melancholy interest to 

 the medical expert and the criminal 

 jurist. In many cases, the decision 

 of court and jury has hinged upon 

 the evidence afforded, or supposed 

 to be afforded, by suspicious stains 

 found upon the clothing or imple- 

 ments used by persons accused of 

 murder. Not very long ago it was 

 imagined by the public, and even 

 by members of the profession and 

 enthusiastic admirers of the micro- 

 scope, that human blood might be 

 positively and easily identified by 

 the microscope. Upon the extension 

 of the scoj)e of utility of the spec- 



*Read before the St. Louis Medido-Chirur- 

 gical Society. 



