TYPHOID FEVER. 1 97 



ir^egula^ and is marked by large and small indentations. 

 There is no liquefaction of the gelatine around the growth. 

 In a test tube cultivation the growth appears all along the 

 line of the puncture and also on the surface. The surface 

 culture has a peculiar mother-of-pearl look, it gradually 

 spreads over the whole of the gelatine, forming a kind of 

 bluish-grey film, whilst down each side of the needle track 

 there is a delicate zone of the same bluish-grey colour, 

 surrounded in turn by a peculiar opalescent milkiness. The 

 most characteristic growth, however, occurs on sterilized 

 potatoes. It is characteristic in that, even when there is a 

 most luxuriant growth of the typhoid bacillus, it cannot be 

 recognized by the naked eye, even at the end of three or 

 four days, except by a peculiar moist appearance of the 

 potato, which, taken along with the appearances in milk 

 and on gelatine so far as is at present known, distinguishes 

 the growth of this organism from all others. It will be 

 remembered, however, that the potato is slightly acid, and 

 it appears that this acidity is necessary for this typical growth, 

 for on potatoes rendered slightly alkaline there appears a 

 yellowish or dirty grey growth with sharply defined margins 

 — a growth quite different from that above described. 

 Chantemesse and Widal utilized the power of the micro- 

 organism to grow in acid to help them to obtain pure 

 cultivations. They prepared special tubes of gelatine by 

 adding to each lo c.c. of the nutrient medium, 4 or 5 

 drops of I to 20 per cent, solution of carbolic or phenic 

 acid ; they did this in order to prevent the development of 

 those microbes that bring about liquefaction of gelatine. 

 They were perfectly successful in their attempts, although, as 

 we have seen elsewhere, it does not follow that their expla- 

 nation was absolutely correct ; at any rate they were able to 

 separate pure t5^hoid bacilli which had all the characteristic 

 appearances both on the gelatine plates and under the 

 microscope. 



The organism itself, unlike many other bacteria, seems to 

 form an acid and not an alkaline excretory product. It 

 grows in a variety of media, and as I have already said, it 

 appears under certain conditions to become quite saprophytic 

 in habit, this being evidenced by the ease with which it may 

 be cultivated outside the body, and quite recently Wolffhiigel 

 found that it may develop readily in both milk and water to 



