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 
