VETERINAEY SCTENCE AND PRACTICE. 401 



"Cheeses of large size usually form soluble nitrogen compounds more rapidly than 

 smaller cheeses under the same conditions, because large cheeses have a higher 

 water coiitent after the early period of ripening. 



"Cheese containing more salt forms soluble nitrogen compounds more slowly than 

 cheese containing less salt. This appears to be due, in part, to the direct action of 

 salt in retarding the activity of one or more of the ripening agents, and in part to 

 the tendency of the salt to reduce the moisture content of the cheese. 



"The use of increased amounts of rennet extract in cheese making, other condi- 

 tions being uniform, results in producing increased quantities of soluble nitrogen 

 compounds in a given period of time, especially such compounds as paranuclein, 

 caseoses, and peptones. 



"Acid is necessary for the formation of paracasein monolactate, from which solu- 

 ble nitrogen compounds appear to be formed in normal cheese ripening; but the 

 exact relation of varying quantities of acid to the chemical changes of the ripening 

 process has not yet been fully studied. 



"Paracasein, caseoses, and peptones usually vary within small limits and do not 

 usually accumulate in cheese in increasing quantities, but after a while decrease, 

 while amids and ammonia are found to accumulate continuously during the normal 

 ripening process. Low temperatures favor some accumulation of the transient prod- 

 ucts, while high temperatures favor the more rapid accumulation of amids and 

 ammonia. 



" The accumulation of soluble nitrogen compounds in cheese appears to diminish 

 the action of the agents causing the changes, so that cheese ripens less rapidly after 

 the first period. 



"An increased moisture content in cheese favors more active chemical change for 

 two reasons: (1) Moisture in itself favors the activity of ripening ferments; (2) the 

 presence of increased amounts of moisture serves to dilute the fermentation products 

 that accumulate. 



"Tlie conditions of the manufacture of cheese and of ripening determine the 

 rapidity and extent to which chemical changes take place in the nitrogen compounds 

 during ripening. The following conditions promote more rai>id change: (1) Increase 

 of temperature in ripening; (2) larger amount of rennet; (3) higher moisture content 

 of cheese; (4) decreased amount of salt; (5) large size of cheese, and (6) moderate 

 amount of acid. Cheese made and handled so as to ripen slowly is of higher com- 

 mei'cial value." 



The regular appearance of different types of strictly anaerobic butyric- 

 acid, bacteria in hard cheese, A. Rodella {Centhl. Bakt. u. Far., ,?. Abt., 10 

 {lOOS), Xoa. 16-17, pp. 499, 500; 24-25, pp. 753-755).— in these two articles, with 

 slightly different titles, the author reports the regular occurrence in numerous 

 samples of several kinds of hard cheese of anaerobic bacteria, especially forms 

 capable of producing butyric-acid fermentation, and describes briefly the methods 

 used in their isolation and culture. It is tlie author's purpose to discuss the relation 

 of the butyric-acid l)acteria to the rii)ening of cheese in a concluding article. 



How can the East compete with the West in dairying? J. L. Hills {New 

 Jei-sei/ State Bd. Agr. L'pt., 1902, pp. 175-201). 



VETERINARY SCIENCE AND PRACTICE. 



Immunity and imraunization, L. Hopf {Immunitdt und Immunisirung. Tubingen: 

 Franz Fietzcker, 1902, ^Jp- VI-\-9G). — A general account of the subject of immunity 

 from a historical standpoint. The author discusses immunity toward various 

 poisons as well as toward infectious diseases. Notes are given on the methods of 

 immunization and on the theories of inununity which have prevailed among various 

 civilized and uncivilized races. The latter part of the v(jlume is devoted to a dis- 

 cussion of the nature of immunity as understood from the recent* investigations of 

 bacteriologists. 



