DETECTION OF SPECIFIC PATHOGENS 



21 



samples are used. Where pint samples 

 are used, standards corresponding to 

 the smaller quantity of milk should be 

 used. 



Preparation of disks for filing. 



After the cotton disks are removed 

 from the filter they are placed on white 

 blotting paper and sprayed with a 

 strong disinfectant such as corrosive 

 sublimate. Good results are secured 

 by using an ordinary throat atomizer 

 provided the caution is observed of not 

 using corrosive sublimate in contact 

 with metal. The disks are then allowed 

 to dry. The drying process may be 

 hastened by placing them in a hot air 

 oven at a drying temperature care- 

 fully protected from dust and flies. 

 When dry they should be compared 

 with the gauge and the results re- 

 corded. They may be filed by placing 

 in paraffin envelopes, or by attaching 

 the disks to heavy paper or cardboard 

 which are then placed in envelopes of 

 suitable size. If the transfer is made 

 to the permanent record sheet before 

 the disks are entirely dry, the dried 

 milk will serve as a very satisfactory 

 glue for attachment. 



Reports. 



Experience has shown that one of 

 the most effective ways of reporting 

 results to dairymen or dealers is to 

 return a half disk or duplicate disk 

 to them with a statement as to the way 

 in which it was obtained. The com- 

 monest criticism that can be applied 

 to the comments sent with such reports 

 is that they frequently make claims 

 regarding the influence of dirt upon 

 the bacterial count which are not 

 substantiated by investigation^^ Dirt 

 of any sort is sufficiently objectionable 

 in milk or any other food to be con- 

 demned solely on the ground that it is 



dirt; and it only weakens the objection 

 to attempt to bolster it by doubtful 

 claims as to the exact correlation 

 between bacteria and dirt. 



The general effect of the use of the 

 sediment test has usually been to 

 cause quickly a noticeable reduction 

 in the amount of visible sediment. 

 However this is accomplished in too 

 many cases by greater care in straining, 

 clarification and the like, rather than 

 by greater cleanliness in the handling 

 of the milk. As "clean" milk is 

 greatly to be preferred to "cleaned" 

 milk some have objected to the use of 

 the sediment test. However, a proper 

 combination of dairy inspection with 

 the sediment test, may be made a 

 very valuable means of securing clean 

 milk. 



(f) detection or specific pathogens 



IN MILK 



There is no part of the field of 

 sanitary analysis of milk where routine 

 laboratory methods have so failed to 

 meet the need of the control official 

 as at this point. Some notable 

 attempts have been made to secure 

 the elimination of the bacillus of 

 bovine tuberculosis from market milk 

 supplies through routine laboratory 

 examinations of milk samples; but 

 none have been found to be sufficiently 

 practical to have been widely followed^^. 

 Other pathogenic organisms, such as 

 those of typhoid fever, are rarely 

 sought for in milk, though methods 

 for detecting this organism have been 

 suggested^'. In all of these cases, it 

 has become necessary to rely on elim- 

 ination of the pathogens in market 

 milk supplies through pasteurization, 

 or by veterinary inspection of the 

 herds, and medical supervision of dairy 

 employees. 



Several of our important control 



