816 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



horse-dung, both of which are abundantly provided with azotized 

 principles, or of the so-called mineral liquids proposed by Pasteur and 

 Cohn. 



The moist chambers used by Van Tieghem and Lemonnier have 

 during the last ten years undergone many modifications, more or less 

 satisfactory ; some investigators have pierced the sides of the little 

 chamber with one or more square holes for the facility of introducing 

 into the interior various reagents, as iodine or ammonia. It is never- 

 theless singular that these observers have overlooked the chance of 

 these holes permitting the access of dust charged with germs. It is 

 not, however, my purpose to give the history of these moist cells, but 

 simply to describe a method of cultivating the bacteria upon the slide, 

 free from these errors, and which I have employed for the study of 

 the atmospheric Schizophytes. The same cell is made use of, pierced 

 laterally by an opening which can be closed by a small glass rod 

 stopper. Fig. 135 represents the same in section, where O is the im- 

 mersion objective, L the thin cover with the droplet attached to the 



Fig. 135. 



under side, H the moist chamber, T the small glass rod stopper, P the 

 stage of the Microscope, and C the condensing lens. The cells and 

 cover should be attached to the slide by a cement that will not be 

 loosened by the heat used to sterilize the chamber. Afterwards, by 

 the lateral opening, one or several drops of sterilized water for the 

 purpose of keeping the air in the cell saturated with moisture, are 

 placed in the little chamber. Then, by means of a pipette with a 

 curved capillary point, the sterilized nutritive liquid — as blood serum, 

 broth, urine, vegetable juices, &c.— is placed upon the under surface 

 of the thin glass cover, whilst the sowing of the organisms, whose 

 development is to be watched, is accomplished by the aid of a fine 

 platinum wire slightly bent at the point. The small rod stopper is 

 replaced, and the whole with the Microscope is placed in a warm 

 chamber kept at 30° C. If immersion objectives be used, a little 

 glycerine can be added to the water, or cedar oil used on the cover. 

 Good dry objectives and the light from a paraf&n lamp generally 

 suffice for the observations, but I give the preference to the excellent 

 1^0. 7 immersion objective of Nachet. It is not necessary that I 



