Journal of Applied Microscopy. 



85 



of 1.8 mm. with 90 mm. petri dishes, 

 plated i cc. of stomach fluid, and used 

 5000 as a factor. For greater accuracy 

 I count ten fields and use 500 as a factor. 



Where I expect the bacteria to num- 

 ber up into the millions per cc. I adopt 

 the following method: 



With an accurately graded sterile 

 pipette, I transfer 1 cc. of the fluid 

 under examination to a flask containing 

 100 cc. of sterile water. Shaking this 

 thoroughly, I take with another sterile 

 pipette one cc. of the dilution and trans- 

 fer to a second flask containing 100 cc. 

 of sterile water, then with a third, and 

 possibly even a fourth flask, the process 

 is repeated. The dilutions in the flasks 

 will be respectively 1:100, 1:10,000, 1:1,000,- 

 000, 1:100,000,000. By making plate cul- 

 tures from each of the flasks, one will 

 be found when the colonies can be read- 

 ily counted by ordinary methods and 

 the proper factor used . This, it seems 

 to me, is an improvement on the custom 

 sometimes in vogue, of designating bac- 

 teria when found in these large numbers 

 as "countless." 



George H. Heald, M. D. 



Instructor in Bacteriology in the Amer- 

 ican Medical Missionary College, Chi- 

 cago, 111., and Director of the Battle 

 Creek Sanitarium Laboratory of 

 Hygiene. 



A Note on the Mounting of Golgi 

 Preparations. 



G. Carl Hubek, M. D. 



A number of years ago I pointed out 

 that Golgi preparations might be 

 mounted under a cover-glass if certain 

 precautions were followed. My further 

 experience with the method then pro- 

 posed, and the fact that some of my 

 preparations mounted some six years 

 ago are still practically as good as when 

 first made, prompts me in again calling 

 attention to this method. 



After the completion of the impregna- 

 tion the blocks of tissue are placed in 

 absolute alcohol twelve hours, equal 

 parts of ether and absolute alcohol, 

 twelve hours; and thin celloidin, twelve 

 hours. They are then blocked on corks 

 in the usual way. As soon as the 

 celloidin is hard enough to cut, sec- 

 tions varying from 25 f.1 to 100 fx 

 (according to the tissue to be studied), 

 are cut into ninety-five per cent, alcohol. 

 The sections are then transferred into 

 absolute alcohol, in which they remain 

 fifteen to twenty minutes. From the 

 absolute alcohol the sections are placed 

 in creosote, which completes the dehy- 

 dration and clears the preparations. In 

 this solution the sections are allowed 



to remain about ten minutes, are then 

 transferred to turpentine, where they 

 should remain another ten minutes. 

 From the latter solution the sections 

 are removed to the slide. The excess 

 of turpentine is now removed by press- 

 ing the sections to the slide with several 

 filter papers. The sections are then to 

 be covered with a relatively large quan- 

 tity of balsam, and carefully heated over 

 a flame, for two, three or four minutes* 

 or until so much of the solvent of the 

 balsam has been driven off by the heat, 

 that the balsam will set as soon as it 

 becomes cool. Before the balsam cools, 

 the preparation is covered with a cover 

 glass, which has been passed through 

 the flame several times before placing 

 it on the balsam. It seems to me that it 

 is only necessary to dehydrate the sec- 

 tions thoroughly and then mount them 

 in hard balsam to insure their keeping 

 without deterioration when mounted 

 under a cover-glass. 



University of Michigan, Ann Arbor, 

 Mich., February, 1898. 



* Huber, Zur Technik der Gologischen 

 Faerbung. Anatomischer Anzeiger, No. 18, 

 Vol. VII. 1892. 



Notes on Microscopical Technique. 



G. Carl Huber, M. D. 



Third Paper. 



SECTION CUTTING. 



In the third article of this series, I pur- 

 pose briefly to discuss the procedure of 

 cutting microscopical sections. But at 

 the outset, it may be well to state that 

 it is as impossible to teach the uninitiated 

 how to cut sections by verbal or written 

 description as it is to teach a boy how 

 to swim by verbal directions. Here, as 

 in everything, "practice makes perfect." 



Before beginning, however, the few 

 hints which it seems to me might be 

 useful to one beginning section cutting, 

 a few words about the microtome and 

 knife may not be amiss. 



Microtome. — In selecting a microtome, 

 which might serve as the basis of my 

 remarks, I am guided by the follow- 

 ing considerations: Cheapness, general 

 applicability, ease of manipulation, and 

 durability. These requisites are, I 

 believe, best met by an instrument built 

 after the Schantze pattern, an instru- 

 ment, which, in the opinion of the writer, 

 will serve every purpose which might 

 be required of a microtome by a physi- 

 cian, and is shown in Fig. I. This instru- 

 ment consists of a frame A, of a slide 

 B, which supports a block C, which in 

 turn supports D, the knife-holder. It is 

 provided with a clamp E for holding 

 the paraffin or celloidin blocks; this is 



