1884.] 



MICKOSCOPICAL JOURNAL. 



225 



quantity, and hope soon to have a like 

 abunchuice of M. prodigiosus. It 

 will be sent on a piece of paper, 

 and the best way to start a culture 

 is to touch the paper to the surface 

 of a slice of boiled potato, or hold 

 the paper above the latter and scatter 

 some of the material over the potato 

 by means of a needle heated to steril- 

 ize it in the flame of a lamp. The 

 paper may also be soaked in a few 

 drops of water and the needle be 

 dipped into the water and transferred 

 to the potato several times. In this 

 way the spores can be transferred td 

 the potato, but there is rather more 

 danger of contamination from other 

 bacteria in the water. 



The best method of obtaining pure 

 cultures of bacteria is to grow them 

 on a solid substratum such as sterilized 

 gelatin, or potato. Inoculating the 

 medium at various points with a 

 needle as already described, the spe- 

 cies will grow from the different cen- 

 tres. From the young growths fur- 

 ther inoculations can be made in the 

 same way, and finally absolutely pure 

 growths are obtained. These can 

 then be cultivated in fluid media if 

 desired. The reader should refer to 

 the article on this subject published 

 on page 185. The forms of culture 

 tubes used for fluid media by Dr. Sal- 

 mon and Dr. Sternberg will be fig- 

 ured next month, the cuts not being 

 ready for this issue. 



The simplest arrangement that can 

 be devised for a culture-chamber is a 

 glass tumbler inverted over a sauce- 

 dish containing water, with a salt- 

 cellar projecting above the water to 

 support the specimen. If a large 

 bell-glass is at hand it is still better, 

 as it will receive several specimens. 



Most of the species will grow well 

 on boiled potato, and it is only neces- 

 sary to cut a slide about one-quarter 

 of an inch thick, touch it with a 

 needle carrying the spores, place it 

 under the glass, and in a day or two 

 abundant growths will be obtained. 

 A small portion placed under a mi- 

 croscope will show the characteristic 



spherical cells of the micrococcus. A 

 high-power objective must be used, 

 however, as the cells are exceedingly 

 minute — nothing less than a j^g-inch 

 will show them clearly, and a ^ly is 

 desirable. 



To distinguish the cells clearly they 

 should be prepared by staining and 

 mounting in water. They stain 

 readily withanilin colors, especially 

 with methyl blue, which is the color 

 we have used for the purpose. The 

 process of preparation is as follows : 

 Having obtained a good growth on 

 the potato, prepare a clean slide and 

 cover-glass, put a drop of water on 

 the slide, take a small portion of the 

 gelatinous growth on the point of a 

 sterilized needle, transfer it to the 

 drop of water, and dry slowly over a 

 lamp. When thoroughly dry, cover 

 the deposit on the glass with a strong 

 aqueous solution of the anilin color, 

 and in two or three minutes wash it 

 oft' with water. The preparation 

 may then be examined in water or 

 glycerin. We are accustomed to use 

 a Spencer J^^-inch objective in this 

 work, with an Abbe condenser. 



The precautions to be observed in 

 preparing the culture-medium will 

 depend somewhat upon the purity of 

 the atmosphere, or its freedom from 

 spores of various kinds. We have 

 succeeded very well by merely cut- 

 ting a boiled potato, while still warm, 

 with a knife-blade sterilized in a flame, 

 and immediately placing the pieces 

 under a bell-jar. If, however, it seems 

 desirable to sterilize the potato, so as 

 to ensure absolute freedom from con- 

 tamination, it maybe done in a man- 

 ner described to us a short time ago 

 by Mr. Theobald Smith. The slices 

 are placed in a solution of corrosive 

 sublimate, i part to 1 ,000 of water, 

 which kills all spores that may be 

 present. The slices are then steamed, 

 and the condensed steam carries away 

 the mercury salt, and whatever is 

 planted will be sure to grow without 

 danger of being overrun with other 

 species. The advantage of the cor- 

 rosive sublimate is that it not only 



