1882.1 



MICROSCOPICAL JO [TRIBAL. 



71 



croscopes, many of which were the 

 long-tubed, complicated models. 

 Very soon, however, they would be- 

 come disgusted with their own pro- 

 perty, and discard the large instru- 

 ment for the one furnished by the 

 College. The objectives required 

 are only two, I think, at least for the 

 beginner ; an one-inch, and an one- 

 quarter or one-fifth inch. Only two 

 oculars are necessary — one with a 

 micrometer-scale. The higher powers 

 are generally employed for the study 

 of amoeboid movements, or some 

 special subject, and a collection of 

 half a dozen immersion one-tenths, 

 with perhaps one or two even higher, 

 will suffice for twenty-four students. In 

 like manner, two or three polariscopes 

 and spectrum-oculars will be all that 

 is needed by two dozen men. Per- 

 haps each man should have a micro- 

 tome, though free-hand cutting is 

 often quicker and better. The freez- 

 ing microtome, I am confident, has 

 but a limited use, provided the tissue 

 be properly hardened. There are 

 many objections to the promiscuous 

 use of the freezing microtome. 



My own experience then, taken for 

 what it is worth — no less, no more — 

 convinces me that a simple micro- 

 scope, and a comparatively few ac- 

 cessories, combined with a desire to 

 learn, and plenty of material, pro- 

 duces the best results in a student's 

 laboratory. 



University of New York. 



Photo-micrograpliy. 



BY PROF. C. HENRY KAIN. 



Photo-micrography, or the art of 

 photographing large views of m.icro- 

 scopic objects, is no new thing, but I 

 doubt whether microscopists in gene- 

 ral are fully aware of the extent to 

 which the late improvements in dry- 

 plate photography have simplified the 

 work. 



To the investigating microscopist, 

 it is almost absolutely essential to be 

 able to permanently preserve the re- 



sults of his observations. This is 

 usually done by the aid of the came- 

 ra lucida, and the zealous worker will 

 often sit for hours with his eye fixed at 

 the instrument, laboriously striving to 

 represent an object, and, if he is not 

 well-skilled in the use of the pencil, 

 his labor is frequently almost useless, 

 so inaccurate is the result. By far the 

 greater part of this kind of labor may 

 be saved at an expense so trifling, and 

 with results so satisfactory, that I 

 think the time is at hand when every 

 working microscopist will regard a 

 dry-plate photographic outfit as a 

 necessary part of his equipment. 



The wet-plate process is cumber- 

 some and not well adapted to the 

 wants of the microscopist; but the 

 dry-plates now in the market are ad- 

 mirable, not only for their great sen- 

 sitiveness and beautiful results, but 

 also for the ease with which they can 

 be manipulated. They can be pur- 

 chased so cheaply that it will scarcely 

 pay the microscopist to prepare them 

 himself. Some of the great advanta- 

 ges which they possess are the follow- 

 ing: 



1. They can be kept for any length 

 of time and used as occasion requires. 



2. If not convenient to develop the 

 plate at the time the exposure is made, 

 it can be put away and developed at 

 leisure, even after an interval of 

 weeks. 



3. No dangerously poisonous chem- 

 icals are necessary in the developing 

 process. 



4. They are so sensitive that the 

 light of an ordinary kerosene lamp 

 (preferably a student lamp), is amply 

 sufficient to photograph objects with 

 all powers not higher than a half-inch 

 objective. Indeed, I think it proba- 

 ble that a quarter-inch objective could 

 be so used by properly arranging a 

 system of condensers. 



The apparatus which I use is a 

 small camera about eight inches 

 square, such as is furnished with the 

 amateur photographic outfits now so 

 popular. To use it for photo-micro- 

 graphy I simply substitute my micro- 



