EXPERIMENT STATION BULLETINS. 



283 



. TABLE X. 



* v. g. — Vigorous normal growth of colonies. 

 t r. g. — Retarded growth of colonies. 

 t n. g. — No growth of colonies. 



From the above table it will be readily noticed that 100 per cent of carbon dioxide 

 has not only a marked retarding influence, but in some instances an inhibitory action 

 where the germs have not grown at all. The retarding action was noticeable in the 

 slow development of the colonies in the plates subjected to carbon dioxide, when in air 

 duplicate colonies developed very rapidly. This restraining action is manifest in five 

 out of eleven. The inhibitory action was determined by allowing the plates to develop 

 in air after removal from the carbon dioxide atmosphere. This inhibitory action 

 existed in six out of eleven. Total inhibition existed in Nos. 123, 125, 127. To what 

 extent the amount of carbon dioxide may exercise any influence is of considerable 

 interest, since we find a great variation in the carbon dioxide in milk as it under- 

 goes the various operations of the dairy; consequently we have carried the work a 

 little farther to ascertain the effect as the percentage is reduced. » 



XIII. DESCRIPTION OF MICRO-ORGANISMS. 



The laboratory numbers used to represent the micro-organisms may be elucidated by 

 reference to a table giving some identifying marks, although in the case of those 

 bacteria obtained from milk directly, no attempt has been made to work out their 

 life histories. They are in every case micro-organisms which have been found more 

 or less constantly in the college dairy, have been used frequently in our laboratory 

 work because of their frequency in the college dairy milk and are therefore repre- 



