EXPERIMENT STATION BULLETINS. 



235 



development. We have shown that heat restrains the growth consider- 

 ably even when placed in favorable temperature for development. It 

 appears to me that by contrasting this table with the table illustrating 

 the time of development in the refrigerator, we shall have gained the 

 desired knowledge. Blank spaces had not developed in 45 days. 



No. of 

 micro- 

 organisms 



3. 



21. 



30. 



48. 

 107. 

 116. 



First test. 



■a 

 cd 

 -^ 

 a 



O) 



A 

 a 



a 3 

 u 



33 

 25 

 33 

 46 

 25 

 25 



CD 

 -^ 



CD 



A 



0° 



75 

 57 

 67 

 100 

 51 

 93 



o 



CD ttl 



A'u 



SS.S 



45 



21 



Second test. 



-3 



OS 



a) 



.3 



a 

 s 





28 

 20 

 20 

 53 

 20 

 22 



rs 

 cd 



at 

 a> 



A 



s5 



-S o 



o 



67 

 48 

 53 

 76 



28 



o 



CD OS 



cd ° 



S be 



- W 33 



a-o J? 



25 



Third test. 



-z 

 o 



CS 

 CD 

 43 



a 



a 



•3W 



24 

 24 

 26 

 46 

 24 

 24 



S 



ts 



CD 



A 



a 3 



aM 

 O 



46 

 26 

 31 

 54 

 32 

 26 



o 



CD CO 



cd ® 

 CD to 



AS 



£ £ « 



a <oQ 

 3 



Fourth test. 



- 



Cu 



4? 



CCS 

 CD 



-= 

 a 



a 



5§ 



29 

 24 

 24 

 45 

 24 

 24 



-n 



CD 



ca 



CD 



A 



5 o 

 u 



45 

 45 

 45 

 70 

 29 

 29 



u 



O 



■°"S 



CD w 

 CD QC 



J3"E 



a-a j. 

 3 . 



42 



Fifth test. 



-a 



CD 

 ~ 

 ad 



CD 



A 



a 



2 E- 



a 2 



o 



21 



7 



6 



46 



7 

 7 



•6 



CD 



S3 

 CD 



A 



a^ 



3« 



46 

 30 

 29 

 94 

 29 

 29 



O 



CD g 



* S. 

 cd cm 



•a'E 



2 ® • 

 ® i. ■ 



fc, •" CO 



a «sQ 



25 



9. Suggestions as to the Reduction of Infection. 



Owing to the fact that these resistant bacteria are found in the milk 

 ducts, in the filth of the barn and in the dairy, I can only advise the 

 general recommendations made in the bulletin preceding this. In suc- 

 cessful dairying, cleanliness must be observed. 



10. The Value of Pasteurization. 



Pasteurization has for its objects, the reduction of the number of 

 bacteria, the enhancing of the keeping quality, and the killing or devital- 

 izing of pathogenic bacteria. 



It is true that the number of bacteria is considerably reduced; but 

 the reduction in the number of harmless bacteria cannot be a practical 

 gain especially when these bacteria (lactic acid bacteria) are more desir- 

 able than those that remain. The lactic acid bacteria check the growth 

 of other bacteria by the formation of acid. If those bacteria remain- 

 ing after Pasteurization (mostly peptonizing bacteria) are allowed to 

 grow for a sufficiently long time, they may produce substances which are 

 not only detrimental many times to the animal economy but even poison- 

 ous. Guinea pigs have been poisoned with the products of these bacteria. 

 A single experiment will illustrate this point. A culture of one of the 

 peptonizing bacteria in milk was taken after the milk had been completely 

 peptonized and made slightly acid with acetic acid. It was filtered and 

 evaporated to a syrupy mass, when it was extracted with alcohol and 

 the alcohol extract evaporated to dryness. The residue was dissolved 

 in the least possible amount of distilled water. One cubic centimeter 

 of this solution killed a guinea pig in a few hours. 



