No. 6. 



DEPARTMENT OF AGRICULTURE. 



&g9 



of food, as from au insufficient amount of dry hay to an abundance 

 of nutritious, succulent food, is accompanied by an increase in the 

 percewtage of fat inluilk, as well as in the yield of milk. 



The writer has noticed (hat, in the case of milk taken to cheese 

 factories, the fat increased very noticeably and generally during 

 the latter half of May, as compared with the preceding portion of the 

 month. In these cases, the cows were commonly fed on timothy 

 hay, without grain, utitil pasturage came. There was thus a very 

 marked change in the character of the food. However, we cannot 

 deny that the more favorable surroundings of the cows at pasture, 

 as compared with the cows kept in the stable or yard, exerted an 

 influence that should not be overlooked. Taking the milk of quite 

 a large number of different cheese factories we found, on an aver- 

 age, during the first half of May, the per cent, of fat was 3.46, aud 

 during the latter half 3.70, an increase of 0.24 per cent, in a brief 

 space of time. 



(h.) Variation of Fat in Different Portions of Milk Drawn from 

 Udder. — In the case of the figures given below, the udder was milked 

 as nearly as possible in four equal portions. 



It 



o 





g- 



a 

 u 

 u 



o ^ 





First portion, 

 Seccmd portion, 

 Third portion. 

 Fourth portion, 



0.90 

 2.60 

 5.35 

 9.80 



1.60 

 3.20 

 4.10 



8.10 



1.60 

 3.25 

 5.00 

 8.30 



It is seen that in every case the first fourth of the milk drawn 

 from the udder is very low in fat, a«id that the fat increases in 

 successive portions drawn, until in the last it is extremely high. 

 The most satisfactory explanation offered for this behavior of fat 

 in. milking is that the fat-globules strike against the sides of the 

 minute ducts, through which they flow, and the friction thus caused 

 holds the globules back, the milk that remains in the ducts becom 

 ing increasingly richer in fat in consequence. 



4. The Nitrogen Compounds or Proteids of Milk. 



(1.) Number of Proteids in Milk. — So far as our present knowledge 

 goes, we appear to be justified in believing- that milk contains not 

 more than four nitrogen compounds or proteid bodies, and these are: 



