120 TESTIMONY OF BENJAMIN SILLIMAN. 



are upon a very different ground of argument, understand, from what 

 we are when speaking of average commercial milk ; I can point you to 

 scores of samples of the milk of individual cows, which will fall low 

 in density, but the average milk of cows does not vary if they are in 

 health ; if you take twenty cows, twelve cows, forty cows, it does not 

 vary substantially from 1.030 ; that science has perfectly determined, 

 unless you select a dozen of cows of very exceptional quality, but if 

 you do the average of any herd under exceptional conditions of 

 temperature or health there may be variations. 



Q. Ought the gravity of the milk of cows to vary much at in- 

 tervals of 10 days ? A. It would depend on their food and the 

 condition of their health ; it may vary very much within that 

 limit of time. 



Q. Now, you say that among the herd of a dozen of cows the 

 gravity of their milk ought to be nearly the same, and ought not to 

 vary much ? A. The average gravity, yes, sir ; I mean that it 

 ought not to vary much from 1.030. 



Q. I now read you the figures from the report signed by Doctor 

 O'Connor, made to the Board of Health, the figures showing the 

 gravity of milks from a herd of thirteen cows, and I ask you whether 

 that is an unusual variance ; the figures are as follows A. The 

 temperature is presumed to be at 60 ? 



Q. I suppose so ; the figures are 101, 108, 116, 118, 113, 103, 

 102, 122, 106, 112, 105, 102, and 114 ; now, sir, assuming those 

 to have been properly made at a standard temperature Fahrenheit, 

 is that an unusual variation in a herd of thirteen cows ; I ask you 

 to assume that the test was properly made at the proper temper- 

 ature. A. I should say that all those cows that were reported 

 there were under abnormal conditions of health or food. 



Q. I am forced to come back to my previous question, Professor 

 Silliman ; I want to make it plain if I can ; I am not talking 

 about commercial milk, but to the kind of milk I referred to, pure 

 milk from two cows ; if you see two cows milked, see their milk 

 properly tested with the lactometer, and at the proper temperature, 

 the milk from each cow stands at 95, may not the low gravity of 

 one milk be caused by the presence of water, and may not the grav- 

 ity of the other milk be caused by the presence of cream in it ? 

 A. I have no knowledge of any samples 



