28 Transactions of the Society. 



sterilized water, previously placed on the perfectly clean cover-glass. 

 This, when dry, is passed three times through the flame of a 

 Bunsen burner or a spirit-lamp, and stained with a drop of fuch- 

 sin or methyl-violet solution. 



From the micro-organisms transferred to the cover-glass before 

 it is dried and stained, from any remnants of the colony which was 

 examined, and from other colonies bearing exactly similar appear- 

 ances, inoculations should be made in test-tubes of nutrient gela- 

 tin and agar-agar. In this way pure cultivations are established, 

 and the microscopical appearances of the growth in test-tubes can 

 be studied. 



The slower growth of the micro-organisms in solid media, and 

 the greater facility afforded thereby for examining them at various 

 intervals and stages of development, is an additional point in 

 favour of these methods ; and the characteristic microscopical 

 appearances so frequently assumed are, more especially in the case 

 of morphological resemblance or identity, of the greatest im- 

 portance. 



The colonies on plates of nutrient gelatin (examined with a 

 low power) of Bacillus anthracis, or of Proteus mirdbilis, the 

 cultivations in test-tubes of nutrient gelatin of the bacillus of 

 septicasmia in mice, and the brilliant and curious growth of Micro- 

 coccus indicus upon nutrient agar-agar may be quoted as examples 

 in which the appearances in sohd cultivations are absolutely 

 pathognomonic. 



As an example of the importance of these microscopical 

 appearances in the case of morphological resemblance or identity, 

 I need only refer to the comma-bacillus of Koch. This bacillus 

 closely resembles in form the comma-bacillus of cholera nostras, 

 and the comma-baciUus of the mouth, as well as a curved bacillus 

 described as occurring in old cheese. From all these bacilli the 

 bacillus of Koch is distinguishable by its mode of growth in 

 nutrient gelatin when cultivated in test-tubes and on glass plates. 



No one, so far as I am aware, has yet been able to demonstrate 

 the existence of a curved bacillus, wJiich is exactly similar hoih 

 morpliologically and hiologically to the comma-bacillus of Koch. 

 We owe, therefore, to the methods of cultivation on solid media 

 thab the presence of this bacillus serves as a reliable index to the 

 existence of Asiatic cholera, although it may bear no causal relation 

 whatever to the disease. 



There are other facts brought to light by studying bacteria 

 by the method of cultivation on the surface of nutrient gelatin. 

 Not only do the colonies differ in size and colour, but sometimes 

 the shapes assumed by the groups of bacilh are very characteristic. 

 These appearances can be very readily demonstrated by making 

 what is called in German a " Klatch-praparat " ; by this method, we 



