CATTI^E 1 141 



ed cows and cow yielding an abnormal milk. It was found that the average 

 quantity of milk obtainable from the udder by milking, after removal of 

 the milk contained in the main ducts was not equal to that previously ob- 

 tained with the milking tube ; the milk which had formed during milking 

 represented 50 % at most of that obtained beforehand with the tube. From 

 the low pressure of the milk in the udder observed after preparing to milk 

 a cow which was developing mastitis, and from the observations of veteri- 

 nary surgeons to the effect that some diseases of the udder are manifested 

 by a reduction of the yield of good milk several days beforehand, the con- 

 clusion is drawn that somewhat abnormal glands are quite well able to form 

 the milk of the first phase, but are inadequate to produce the milk of the se- 

 cond phase with sufficient rapidity. If the milk does not go down, or if 

 it takes some time to descend, or if it descends in a smaller quantity than 

 usual, it may be concluded that the cow is contracting mastitis, unless the 

 reduction of the milk yield is due to nervous influences. 



To illustrate the mode of formation of milk, the Author represented 

 by curves the quantities of milk obtained by fractional milking of several 

 cows. He was thus able to show that towards the end of milking more milk 

 is drawn than is formed, so that after some time it is not possible to draw 

 any more milk from the udder ; the cow is then completely milked. 



Experiments were also conducted with a view to determining the quanti- 

 iy of milk contained in the main duct and in the teat canal. In this 

 case also the data contained in the literature of the subject diverg- 

 ed. It was formerly generally believed that the main duct alwa^-s contains 

 a large quantity of milk, but latterly the statement sometimes appears that 

 the main duct and canal of the teat do not contain milk during the period 

 of rest. The writer was able to ascertain, in the case of about 100 cows, 

 that all normal teats contained milk in their duct, and that the most swol- 

 len teats contained the smallest quantity of milk. 



The fact that during the period of rest the milk does not pass out of 

 the teat is due to the veins which swell and shut off the exit. Therefore 

 milking is only possible when the blood has been expelled from the veins 

 by specific excitation. 



The teat canal never contains milk during the period of rest. 



S85 - Effect of Water in the Ration on the Composition of Milk. — Turner \v. e., 



ShawR.H., Norton R. 1'., and Wright P. A. — Jmirnul ui Ai,iicullur(il Rcscarcli, 

 Vol. VI, No. 4, pp. 167-178. Washington, D. C, April 21, 1916. 



Experiments conducted at Brownsville, Tex., by the Dairy Division 

 of the Bureau of Animal Industry, U. S. Department of Agriculture indi- 

 cate that the feeding of prickly-pear (Opuntia spp.) lowers the percentages 

 of fat in milk. In comparison with other feeds, prickly-pear contains a 

 large amount of water and mineral matter. It was thought by the writers 

 that one or both of these constituents might be responsible for the re- 

 duction in fat percentage ; consequently experiments were conducted to 

 determine the influence of the water ; work on the mineral matter is 

 in progress. The literature dealing with the effects of watery feeds or 

 water in the ration upon the quantity of milk produced is reported to con- 



