84 



Journal of Applied Microscopy. 



stethescope, the clinical thermometer, 

 the probe, etc. It is now maintaining 

 the hig-hest rank among instruments of 

 research. 



The microscope is of great value on 

 board the ships of our navy. The "flag- 

 ship," the ship that the admiral or com- 

 mander-in-chief of a fleet or station is 

 attached to, is furnished with a micro- 

 scope as part of the equipment for the 

 medical department of that ship. The 

 other ships, as a rule, are not furnished 

 with any, but can easily obtain them 

 by the senior medical officer applying 

 for them to the department. Reports 

 of investigations and research must be 

 made and specimens sent to the depart- 

 ment from time to time. 



The department issues microscopes 

 with 1m, i.i, and l-12ii objectives and a 

 fine list of accessories, especially made 

 for the bureau. By means of these the 

 acts of sharks ("land sharks") and im- 

 purities and adulterations can be easily 

 discovered, which would otherwise re- 

 main unobserved. 



The following are some of the more 

 common: starch of various kinds, improp- 

 erly added to cocoa and mustard; wil- 

 low is sometimes substituted for tea; 

 chickory is found mixed with almost all 

 coffees. Chickory, if not added in too 

 large quantities, rather improves than 

 injures the aroma or flavor of coffee. 



The more important uses of the micro- 

 scope on board ship are as follows: 

 Milk is of such a nature at some ports 

 that the examination of it may save the 

 outbreak of an epidemic, such as typhoid 

 fever. This fever was brought on board 

 one of our battleships recently, and its 

 only source was from milk obtained 

 ashore where disease existed. 



The Examination of Sputum. — Some 

 difficulty is experienced in this exam- 

 ination, as sputum is liable to con- 

 tain many particles which did not come 

 from the lungs, such as fragments of 

 food, scales from the tongue and mouth. 

 The degree of catarrh can be easily 

 determined in this way, as during the 

 progress of the disease the inflamma- 

 tion of the mucus tract and the number 

 of leucocytes becomes more and more 

 abundant. When the lung is breaking 

 down fragments of pulmonic tissue may 

 be readily recognized under the micro- 

 scope by the characteristic elastic fibers, 

 which are rendered very distinct by the 

 addition of acetic acid or previously 

 boiling with a solution of caustic soda 

 (20 grains to the ounce) which clears 

 matter, leaving tissues untouched. 

 Tuberculosis is also recognized by the 

 presence of the tubercle bacilli. 



Urine.^The examination of urine is 

 made to a large extent by the micro- 

 scope. It is important to know the age 



of sample examined, as the changes are 

 sometimes misleading. A portion of the 

 urine passed in twenty-four hours should 

 be taken, and especially that which is 

 passed in the morning. Frequently an 

 examination for several successive days 

 is necessary, for there are conditions of 

 kidney disease in which few casts are 

 passed and would probably escape in 

 one examination. 



The microscope is much used in the 

 examination of tumors, abscesses, gon- 

 orrheal discharge, and many forms of 

 bacteria which I cannot mention here 

 for want of time. In establishing the 

 great truth which connects physiology 

 and hence pathology with anatomy, and 

 in maintaining and following this truth, 

 the microscope ranks highest of our in- 

 struments of research. 



Wm. H. Myers, Ph. G., 



Apothecary, U. S. Navy. 



U. S. S. S. Terror, April 8, 1898. 



A Scheme for Counting Colonies 

 of Bacteria in Petri Dishes when 

 the Colonies are Small and Very 

 Numerous. 



I have for the past two years used the 

 following method of estimating the 

 number of bacteria per cubic centimeter 

 in stomach fluid, in the Laboratory of 

 Hygiene of the Battle Creek Sanitarium. 

 Sometimes the bacteria number up into 

 the hundreds of thousands and even 

 millions per cubic centimeter, and the 

 ordinary methods of counting are not 

 applicable. 



Making use of the principle that cir- 

 cles are to each other as the squares 

 of their respective diameters, I proceed 

 to find a microscopic field which bears 

 a definite ratio to the size of my petri 

 dishes. For instance, my petri dishes 

 have an internal diameter of 90mm, and 

 I find by means of a stage micrometer 

 a field in the microscope which has 1.5, 

 1.8, 3.0, 3.6 or 4.5 mm. diameter. By 

 means of the proper objective and ocu- 

 lar and by lengthening and shortening 

 the draw tube, a field of the proper 

 diameter can be obtained. Then a mark 

 can be made on the draw tube for future 

 use, or a memorandum can be made 

 something in this manner: B. and L. 

 Microscope No. 42756, objective i inch, 

 ocular No. 1, draw-tube 163 mm.=2500 

 fields to a 90 mm. petri dish. 



To ascertain the proper factor (or ratio 

 existing between the microscopic field 

 and the petri dish) use the formula 

 d-^d'=f in which d = diameter of petri 

 dish; d'= diameter of microscopic field: 

 f^ factor. In my work I used a field 



