74 



SCIENCE. 



same plane, the third from the ventral, the fourth 

 from the dorsal extensions of the common nucleus. 



I would call attention to the fact that the average 

 dimensions of the cell nuclei of the auditory nerve 

 nucleus equal those of the motor nuclei of the me- 

 dulla and cord, and exceed some of them, and that 

 the same statement applies to the cells as a whole. I 

 make this statement in view of the recent communi- 

 cation of Dr. Mason before the American Neurologi- 

 cal Association, though I do not claim to make it on 

 the same basis of careful and extensive micrometric 

 observations that his communication was based on, 

 but on a general impression derived from repeated ex- 

 aminations which I think are sufficient to determine 

 palpable differences. 



The present preliminary report is taken from a 

 communication made by me ! o the Journal of Ner- 

 vous Diseases for last June, but I trust before long to 

 submit to your readers a more exhaustive and illus- 

 trated record of this interesting and suggestive piece 

 of cerebral anatomy. 



DRY "MOUNTS" FOR THE MICROSCOPE. 



BY PROFESSOR H. L. SMITH, HOBART COLLEGE, N. Y. 

 II. 



In a former paper, Science No. 3, I made a few 

 remarks upon this subject, and described the methods 

 which I had found tolerably successful, viz.: the rings 

 made of shellac and lampblack, and those punched 

 out of gutta-percha tissue. The former appear to 

 answer quite well, and the changes, if any, are very 

 slight, yet I have, in a very few cases, observed a de- 

 terioration after the lapse of a year or so, probably 

 from imperfect manipulation. Although I have not 

 myself observed any great change in the gutta-percha 

 mounts, I am not certain that they will stand prolonged 

 use with immersion objectives without injury. I have 

 mounted many specimens of delicate test objects for the 

 Messrs. Spencer, and they are decidedly of the opinion 

 that the shellac ring is the better for durability, and I 

 am informed by Mr. Gundlach that the gutta-percha 

 ring will not stand cedar oil. Mr. Phin has suggested 

 that in time the gutta percha tissue will disintegrate. 

 I have not yet noticed this, and do not think it will 

 happen under the cover of a " mount " especially if 

 protected by a ring of cement subsequently applied 

 If, however, such disintegration docs, in time, happen 

 to the tissue, this will be a great objection to its use. 

 I have found that the "tissue" becomes so charged 

 with ele< Hi' it) by handling, and also by the punching, 

 that it interferes seriously with the latter operation, 

 and thus makes it necessary to place strips of the 

 "tissue" on thin moistened strips of paper, and to 

 punch out both at the same time. The preparation 

 of the shellac rings by the turn table obliges one to 



keep on hand a large stock all the time to insure per- 

 fect drying, and to have them always ready. I am 

 obliged to have some 1000 or 1500 on hand in ad- 

 vance, and this necessitates a considerable outlay in 

 stock, which will not always be convenient for ama- 

 teurs. For the above reasons I now propose a new 

 process which appears to meet all the desired wants, 

 and which combines the advantages of the shellac 

 cement and the gutta-percha rings. 



The very simplicity of this process causes me to 

 wonder why it was not thought of before. I take a 

 sheet of thin writing paper, white or colored, and dip 

 it into thick shellac varnish (shellac dissolved in 

 alcohol), and hang it up to dry. When thoroughly 

 dry it should have a good glaze of the varnish on it 

 (different thickness of paper can be used according to 

 depth of cell required). Out of this shellac paper I 

 cut my rings, and these can be made in any quantity, 

 and kept for any time. The process 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 several 

 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 finger and thumb of the two hands, 

 and pressing them tightly together, to warm the slide 

 gently ; by looking at the ring obliquely, on the under 

 side, one can tell at once, 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 moderate heat, and there 

 will be no danger of breaking the cover, unless it has 

 been warped in the process of warming, which will 

 sometimes 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 induce the 

 leading opticians to manufacture 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 under side the name of the preparer, 

 or of the object. I cannot conceive of anything 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 per- 

 fectly protected by the paper rings. I am satisfied 

 that the balsam mounts will be much less frequently 

 used, as soon as we can find some sure dry process. The 

 diatoms, as a rule, show much better when mounted 

 dry, and with whole frustules, exhibiting both the side 

 and the front view, also the mode of attachment, etc. 

 The dry mounts are certainly to be preferred when they 

 are desired for anything except pretty 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 lor any very great 

 length of time, yet I can see no reason why they 

 should not be equal to the simple shellac ring for dur- 

 ability, and very much superior to it in other respects. 



