172 Report of the Department of Bacteriology of the 



pregnant at the time this experiment began although she had been 

 served a number of times previously. She was giving a small amount 

 of milk which decreased slightly during the experiment. She was 

 dried off six or seven weeks after the end of the experiment. Her 

 next calf was dropped in October, 1911. Millie D.'s milk contained 

 large numbers of cells at all times and showed some marked fluctua- 

 tions (see Table XIV and Graph IV, upper portion). At times it 

 was decidedly salty to the taste and did not stick well to the slide 

 when the smears were made for counting the cells. It can scarcely 

 be claimed, however, that these conditions were due to the experi- 

 ment as they are common conditions in the milk of cows which are 

 near the end of their period of lactation. Moreover, the conditions 

 in the control animal were somewhat similar. Mabel S. F. (control) 

 had aborted her calf on October 28th of the fall previous and was 

 giving only a small quantity of milk, the amount of which showed a 

 gradual decrease during the experiment. She, like Millie D., was 

 milked but seven or eight weeks after the experiment closed. The 

 cell content of her milk was never as great as that of Millie D.'s milk 

 and showed a marked decrease toward the end. The same difficulty 

 in making smears of her milk was met with as in the case of Millie 

 D., but no salty taste was noted. 



If the records of the experimental animals are compared among 

 themselves, it is seen that they present equally contradictory con- 

 ditions. Thus the record of Ruth F. shows a gradual increase in 

 the number of the cells in her milk during the period when the 

 vacuum was being increased 1 inch per week. However the record 

 of Gerty F. 2 shows that the number of cells in her milk gradually 

 decreased during the same period, while Millie D.'s record shows 

 an increase in the number of cells in her milk up to the last week 

 of the experiment when a sharp decrease occurs just at the time 

 when the vacuum used was greatest in amount. It is especially 

 noteworthy that exactly contradictory conditions were found in 

 the three experimental animals during the last few days, when the 

 vacuum was being decreased one inch at each successive milking. 

 Graph IV shows, that during these days, the curve for Ruth F. 

 reaches a maximum, the curve for Millie D. a minimum while that 

 for Gerty F. 2 maintains a practically straight course. 



It is thus clearly seen that these changes in the vacuum did not 

 influence the number of the cells discharged and there is no indi- 

 cation that more extensive experimentation would have done so. 



