388 Journal of Applied Microscopy. 



such media as formalin, but in my own experience the latter has not proven 

 satisfactory, and in certain exceptional cases I have not as yet found anything 

 adequate. For example, the Vorticellidae are, so far as my own experience goes, 

 not easily killed in an expanded condition by any medium known to me. In 

 such cases resort must be had to some method of narcotisation, such as the 

 gradual addition of dilute solutions of chloral hydrate, potassium sulphate- 

 nicotine, etc., which may render the organism less sensitive to the action of the 

 fixing agent. In some cases this has been found to work most admirably, while 

 in others it has just as signally failed. 



The organisms finally fixed, they are next to be washed in water or dilute 

 alcohol, as may be found best, then stained by some one of the usual methods, 

 dehydrated in the usual way, cleared by the use of some one of the oils — cedar, 

 clove, etc., and finally mounted in balsam, or, if preferred, in glycerine or glycerine 

 jelly, in which cases attention must be directed to the different preliminary 

 operations necessary. 



At each stage of preparation similar precautions must be observed as to 



transfer from one medium to another, as have been suggested in the original 



transfer from the water to the killing medium. With reasonable care this will 



not be found a difficult matter, though of course some loss must be expected. 



With material thus prepared, the work of permanently mounting is comparatively 



simple, and the results worth all the pains which may have been involved in the 



preparation. I have permanent preparations of such organisms as Amoebam, 



Paramoecium, Volvox, etc., in beautifully expanded conditions, and exhibiting 



almost every phase of life-history peculiar to the several forms. 



Charles W. Hargitt. 

 Syracuse University, May 20, 1899. 



A Method for Extracting Air and Other Gases from Objects. 



One often finds, after killing and hardening any small animal, that some part 

 of it, commonly the intestine, contains air-bubbles. Also, in decalcifying small 

 calcareous animals with acids, especially when one hurries the process, bubbles 

 of C02 are not infrequently formed. At all events, whatever the origin of the 

 bubbles, their presence is adverse to obtaining perfect sections and series. 



Such bubbles of gas can be most readily removed by the following process. 

 It is well known that water contains a considerable quantity of air and some other 

 gases in solution, and that these can be removed by boiling the water. Boil, 

 therefore, for a short time, several hundred cc. of water, and while this is still quite 

 hot pour it into a bottle with a tightly-fitting stopper, leaving little or no air between 

 the water and the stopper. When the water has become cooled to a lukewarm 

 temperature, place the objects in question into the water and cork the bottle 

 tightly as before. After several hours (two or three to twenty-four hours) the 

 water will have absorbed all the gas and the object will have settled to the bottom. 

 Should the object still contain gas, repeat the operation. Should one fear that 

 the object suffer injury, normal salt solution, or alcohol, might be suggested. 

 Unfortunately, however, alcohol contains but little gas in solution. 



I have often used the above method with good success, as have others also, 

 at my suggestion. E. W. Berger. 



Johns Hopkins University. 



