140 PRODUCTS OP VITAL ACTIVITY. 



open for five to eight hours ; the llask is then closed and kept at 18 C. It 

 should be shaken every two hours. At the end of twenty four hours the 

 milk is poured through a fine sieve into another flask, which must not be 

 more than four-fifths full. This is corked and allowed to stand, being 1 

 shaken from time to time. At the end of twenty-four hours a drink is ob- 

 tained which contains but little COa or alcohol. Usually it is not drunk 

 until the second day, when, upon standing, two layers are formed, the 

 low r er milky, translucent, and the upper containing fine flakes of casein. 

 When shaken it has a cream- like consistence. On the third day it again 

 becomes thin and very acid. 



" The second method is used when one has a good kefir of two or three 

 days to start with. Three or four parts of fresh cow's milk are added to one 

 part of this and poured into flasks which are allowed to stand for forty- 

 eight hours with occasional shaking When the drink is ready for use a 

 portion (one-fifth to one-third) is left in the flask as ferment fora fresh 

 quantity of milk. The temperature should be maintained at about 18 C. ; 

 but at the commencement a higher temperature is desirable. The Jcorner 

 should be carefully cleaned from time to time and broken up to the size of 

 peas. The cleaned korner may be dried upon blotting paper in the sun or 

 in the vicinity of a stove: when dried in the air they retain their power to 

 germinate for a long time." 



Fermentation of urea. The alkaline- fermentation of urine is 

 effected by various microorganisms, but chiefly by the Micrococcus 

 urese, the ferment action of which has been carefully studied by Pas- 

 teur, Duclaux, and others. The change which occurs under the 

 action of the living ferment was determined by the chemist Dumas 

 as long ago as 1830, but it remained for Pasteur to show that this 

 change depends upon the presence and vital activity of a living 

 microorganism. 



The transformation of urea into carbonate of ammonia is shown 

 by the following formula : COH 4 N 2 + 2H 2 O = CO, + 2NH 3 + 

 H 2 = (NH 4 ) 2 C0 8 . 



According to Van Tieghem, Micrococcus ureaB continues to grow 

 in a liquid containing as much as thirteen per cent of carbonate of 

 ammonia. It may be cultivated in an artificial solution of urea, with 

 the addition of some phosphates, as well as in urine. 



The Bacillus urese of Miquel has also the power of producing the 

 alkaline fermentation of urine, but it does not thrive in so strong a 

 solution of carbonate of ammonia. 



A different micrococcus Micrococcus urese liquef aciens nas also 

 been studied in Flugge's laboratory which possesses the same power. 

 According to Musculus, a soluble ferment may be isolated from urine 

 which has undergone alkaline fermentation, which changes urea into 

 carbonate of ammonia. He obtained it from urine containing con- 

 siderable mucus, in a case of catarrh of the bladder. But Leube has 

 shown that cultures of Micrococcus urese from which the micrococ- 

 cus was removed by filtration through clay do not induce alkaline 

 fermentation. The soluble ferment obtained by Musculus must 

 therefore be from some other source. 



