292 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
continues high for a time after the clinical symptoms 
have disappeared. The increase of catalase in mastitis 
is not always due to the bacteria present. Koning has 
demonstrated that the streptococci of mastitis do not pro- 
duce catalase, but that the toxins they excrete irritate 
the gland tissue and cause an increased transudation of 
blood serum and emigration of leucocytes, thus increas- 
ing the catalase in the milk. The catalase may also be 
increased in purely traumatic or non-bacterial mastitis. 
When only one quarter of an udder is visibly diseased, 
the milk from the other quarters which are apparently 
healthy may show a high catalase reaction. The catalase 
test cannot be relied upon to discover mastitis when mixed 
milk is examined. Mixed milk containing 5 per cent. 
of milk from a diseased udder will show a high oxygen 
reading, but if the dilution is greater than this there will 
be nothing abnormal in the reaction (Gerber). 
In general disease, and when disease is present in 
other organs than the udder, the oxygen reading of in- 
dividual milk is usually, but not always, high. In these 
conditions, according to Mogendorff, the catalase in the 
milk is increased when the udder assists in the elimina- 
tion of the products of disease, the toxins or other disease- 
products irritating the gland tissue and causing an un- 
usual amount of blood serum and leucocytes to pass over 
into the milk. The presence of pathological processes in 
the body is often indicated by an increase in the catalase 
in the milk before they are manifested by clinical symp- 
toms, while in diseases in which resolution is not complete 
the catalase may be increased in the milk after all clinical 
symptoms have disappeared. As a rule, there is an in- 
crease of catalase in the milk in all diseases accompanied 
by a high fever; when non-encapsulated purulent areas 
