40 THE AMERICAN MONTHLY [Fehrnarj, 



ing the flask. The cover E is in the form of a hood, beneath 

 which steam may escape. Tiie space between the hood and tlie cham- 

 ber averages about an inch, thus keeping the latter en\eloped with steam 

 on the outside as well as filled within. This takes the place of felt, 

 which is used in some other sterilizers. The water which forms inside 

 the hood from condensation drops down into the tank A. This con- 

 densation takes place on the interior surface of the hood but not on the 

 exterior surface of the sterilizer. 



The apparatus without stand is lo inches deep and 9 inches in diam- 

 eter, and holds about 5 gallons. It maybe usecl for disinfecting as well 

 as for sterilizing and for cooking. 



The portability of the apparatus, its simplicity, the ease with which 

 the water may be replenished without discontinuing the process, its 

 compactness and varied utility make it worthy of commendation. 



MICROSCOPICAL MANIPULATON. 



Demonstrating the Influenza Bacillus. — Dr. Pfeifter of the 

 Koch Institute manipulates the sputum of influenza patients by first 

 sterilizing and cleansing it by Koch's methods, and then treating 

 it with Ziehl's solution or Loeffler's hot methylene blue. The two 

 extremities stain more intensely than the intervening parts causing 

 some resemblance to diplococci and to streptococci. 



The bacilli may be then seen under the microscope, being more 

 copius in the mucus and cells of sputum — in the latter, often degenerate. 

 One of their characters is immobility. They are much smaller than 

 :mv otlier known micro-organism. 



Determining Magnification. — A fellow of the Royal Astronomi- 

 cal Society writes to the English Mechanic as follows : 



The magnifving power of a microscope is never found by calculation, 

 being always determined experimentally. 



A micrometer ruled to looths and loooths of an inch is placed on the 

 stage and carefully focussed. Then a rule d'ivided to loths of an inch 

 is held parallel with it at a distance of 10 inches from the other eye and 

 shifted about until the micrometer lines coincide with divisions on the 

 rule. If a division of one-hundredth of an inch corres2:)onds with i^ 

 inches on the rule, the microscope magnifies 150 diameters. 



A more accurate way is to project the image of the micrometer, by 

 means of a camera lucida, 10 inches from the eye and measure this with 

 compasses ten times along the rule. If one of the thousandths divisions 

 on the scale repeated 10 times along the rule measures 6.25 inches then 

 one such division measures .635-inch and the microscope magnifies 

 62s times linear. The very thickness of cover-glass alters the niagnifv- 

 ing power, as does of course any alteration in the length of tube. 



T'he following ^\\g^ items are from the Observer o'i Y)cc.^\v\ntx : 



To detect air bubbles. — The small buljbles which get under the 

 cover-glass while mounting may be detected hy laying the slide on a 

 sli]) of dark-colored glazed paper. View with a lens if necessary. 



To clean objectives. — Use small pieces of Japanese filter paper, 

 which costs but a few cents, foi" this purpose. 



