SPOROGENES TEST. 7 



In order to show the value of the Weinzirl test, the samples of 

 milk have been grouped on the basis of the test in accordance with 

 his arbitrarily assumed standards. Weinzirl's standards were as fol- 

 lows : One gram of manure in 50 liters of milk is excessive ; not 

 more than 1 gram in 100 liters of milk is fair; and not more than 1 

 gram in 150 liters represents good market milk. 



On the basis of this classification, all the samples represented by 

 sediment disks in Plate IV would be classed as good milk. Un- 

 doubtedly such a classification is incorrect. Particular attention is 

 called to the differences in the quantity of manure among samples 

 showing the same results with this sporogenes test. Compare, for 

 example, Samples 1 and 15. In neither case were any positive reac- 

 tions recorded. 



The sediment disks on Plate V were made from milk which would 

 be classed as fair or as having an excessive quantity of manure, 

 according to Weinzirl. The last three samples are the only ones 

 which would be considered to have an excessive amount of manure. 

 It is evident that, with the exception of Sample 36, the rest of the 

 samples at least do not represent good milk, and are certainly no 

 better than the fair milk as classified by the Weinzirl test. Many of 

 these samples of so-called fair milk, however, were evidently much 

 better than some of those classed as good milk. 



As in the Savage method, there is also no definite relation between 

 the Weinzirl sporogenes test and the total bacterial count. Par- 

 ticular attention is called to the variation between the test and the 

 amount of sediment. This is especially striking in the case of Sam- 

 ples 15 on Plate IV and 36 on Plate V. Sample 15 had an excessive 

 quantity of manure showing a negative sporogenes test, while Sam- 

 ple 36 had a small amount of sediment and yet gave a positive reac- 

 tion in the 5 c. c. tube. Positive tests among the three quantities of 

 milk used seem to show no consistent behavior. If a sufficient number 

 of spores are present in the milk to give a positive test in the 5 c. c. 

 tube, the 10 and 15 c. c. tubes should also be positive. If the 10 c. c. 

 tube is positive, the 15 c. c. tube should also show the reaction, but 

 such is not always the case. These variations probably are due either 

 to an uneven distribution of spores or to their failure to develop a 

 characteristic stormy reaction. Weinzirl, of course, merely assumed 

 an arbitrary standard for grading milk on the basis of the sporogenes 

 test, but whatever standard is accepted it would not change the lack 

 of correlation between his methods of making the sporogenes test and 

 the quantity of manure actually in the sample. 



DEFECTS IN THE SPOROGENES TEST. 



Besides the variations in results obtained by repeating the sporo- 

 genes test on the same samples of milk, the test is defective because it 



