566 Journal of Applied Microscopy. 



water with amoebae. The bacilli develop along the stroke in a line which is gradually 

 eaten from below by amoebce. This process can be observed under the micro- 

 scope in a petri dish. Close to the border line between the eaten and not-eaten 

 parts of the line of cholera growth, most of the amoebae are seen. Other bacteria 

 inoculated with the amoebae are, as a rule, not developed, but if others are found 

 a fresh culture is made. To prevent the growth of the undesirable forms over 

 the surface of the culture, it was found efficacious to keep the tubes in the incu- 

 bator for the first day, and after that at room temperature. To obtain pure 

 cultures of amoebae, such mixed growths are treated with acid and alkalies. 

 This kills the cholera bacilli while the amoebae withdraw into cysts. If a 

 sterilized silk thread dipped into this mixture of amoebae and cholera bacilli, is 

 dried in a sulphuric acid drier, amoebae alone remain living. These threads can 

 then be used to make pure cultures. By inoculation from the cyst on gelatin or agar, 

 the vegetative form is obtained, but no increase in numbers ; this occurs alone in 

 the presence of living or dead bacteria. Cover-glass preparations are made by 

 mixing a small amount of culture with a platinum loopful of concentrated 

 solution of acidified chinin. After spreading and drying in the air, it is treated 



with alcohol ether mixture, dried, and stained with methylen blue. 



A. M. c. 



. , ^, , , In order to recognize and distinguish 



Determaan. Khnische Untersuchungen ueber ° 



Biutplattchen. Deutch. Arch. f. Klin. Med. the separate blood plates, as well as to 

 61: 365-411, 2 pis, 1898 (Abst. in Zeit. determine their numerical relations to 

 f. wiss. Zool. 16: 86-88, 1899.) , , , 



the blood corpuscles present, the two 



conditions of massing and easy fragmentation must be considered. A simple 

 addition of preservatives is not sufficient, as this causes a massing of the plates 

 and change in their form. The desired result was obtained by pricking the 

 finger and putting a drop of fixative on the spot. The blood first appearing is 

 thoroughly mixed on a cover-glass with the preservative. Further dilution, if 

 necessary, is made on the cover. From such a preparation the number and 

 numerical relations can be easily determined, if care is taken to count the plates 

 in the whole thickness of a preparation. For a preserving and diluting liquid the 

 author used chiefty a .9 per cent, solution of ordinary salt, to every ten cc. of 

 which had been added a drop of concentrated aqueous, well filtered methyl violet. 

 A mixture of one per cent, sodium chloride with five per cent, bichromate of 

 potash was also very successful. Of many other fluids the author preferred the 

 following: Distilled water 160 g., glycerine 30, sodium chloride 1.0, sodium 

 sulphate 8, methyl violet, .025 (according to Marchner). This was particularly 

 good since it stains leucocytes and blood plates slightly, but enough to render 

 their recognition easy. The plates vary in form from rods to round or oval 

 discs, but after a short time they lose their shape, swell, and finally disintegrate. 

 For dried preparations the best stain was found to be a concentrated solution of 

 methylin violet. Of chemical reagents used, aqueous solutions were found to act 

 in the same time on both the plates and the corpuscles, taking haemaglobin out of 

 the latter. Corpuscles remain morphologically complete for some time, but the 

 plates swell three or four fold, become globular, and finally break up in five to ten 

 minutes. Weak acetic acid preserves the plates as long as the red corpuscles, 

 and the leucocytes last longer than either. 



