106 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



" milks hard," i.e.> that there is difficulty in expressing 

 the milk through the teat canal, or that the milk is not 

 "let down " or is " drawn up," or that the cow has recently 

 developed a tendency to kick during milking, should ex- 

 cite suspicion of the presence of the disease. The first 

 condition is due to obstruction of the teat canal by swell- 

 ing of the mucous membrane or by dried secretion; the 

 others occur because milking is painful. Among the 

 first noticeable symptoms of the disease are changes in 

 the milk stream expressed from the teat. This may be 

 split, deflected from the proper direction, or it may not 

 be cut off promptly and may therefore smear the end of 

 the teat all indications of catarrh of the mucous mem- 

 brane of the teat canal. In such cases small yellow crusts 

 may be found covering the opening of the teat canal, but 

 crusts of dried milk may also be present at this point when 

 the sphincter of the teat canal does not close properly. 

 When pressure is exerted upon the lower end of the teat, 

 a drop of pus or mucus may be squeezed out of the teat 

 canal or the thickened mucous membrane may project 

 through the opening. Later, the mucous membrane of 

 the cistern may become thickened, in which case a cord 

 about as thick as a lead pencil is felt running through the 

 middle of the teat when the teat is rolled between the 

 thumb and fingers. Flat, disc-shaped thickenings about 

 the size of a quarter dollar and nodular indurations may 

 be present in the upper limits of the cistern when the 

 mucous membrane of the lower end of the large milk 

 ducts is thickened. Growths upon the wall of the cistern 

 or teat canal (" spider in the teat ") may also be dis- 

 covered by palpation. The induration usually extends 

 slowly into the interstitial tissue, generally from the teat 



