NUMBER AND SIGNIFICANCE OF LEUKOCYTES IN MILK 489 



very long chains, and does not liquefy gelatin. Some of the stems 

 isolated from cases of bovine mastitis form acid in sterile milk and 

 coagulate it, others do not form acid, nor lead to coagulation. In 

 considering the pathogenicity to man of streptococci found in cattle, 

 it must be remembered that the streptococcus generally found as 

 the cause of suppurative processes in cattle and known as the Strepto- 

 coccus pyogenes bovis is not fully identical with the Streptococcus 

 pyogenes found in man, from which it differs in certain cultural and 

 other characteristics. (See chapter on Pyogenic Bacteria in Domestic 

 Animals.) 



Staphylococci have likewise been frequently found in inflammation 

 of the udder of the cow, and Guillebeau has distinguished the follow- 

 ing four types : Staphylococcus mastitidis, Galactococcus versicolor, 

 Galactococcus flavus, and Galactococcus albus. Lucet has described 

 five different staphylococci of bovine mastitis, but he has not proposed 

 special names for them. Mastitis in the cow has been produced 

 experimentally by the injections of Bacillus suipestifer, Streptococcus 

 equi, Bacillus avisepticus, and Botryococcus ascoformans. 



NUMBER AND SIGNIFICANCE OF LEUKOCYTES IN MILE. 



Milk always contains certain cellular elements. The fluid secreted 

 during the very first stage of lactation, called colostrum, shows 

 corpuscles filled with fat granules known as colostrum corpuscles. 

 The derivation of these bodies has been a contested question for a 

 long time, but the preponderance of evidence now appears to be that 

 the majority of them are mononuclear leukocytes, and only a small 

 number are granular epithelial cells, both filled with fat granules. 

 The colostrum corpuscles disappear soon after the beginning of 

 lactation, and the most important cells always found in milk are the 

 leukocytes, or white blood corpuscles. Several authors, among those 

 who have studied the significance of the number of leukocytes found 

 in milk under various conditions, have very seriously discussed the 

 question how to distinguish in milk between leukocytes and pus 

 corpuscles. This must appear somewhat futile in view of the fact 

 that there is no generic difference between a leukocyte and a pus 

 corpuscle. Histopathologic investigations have shown beyond doubt 

 that a pus cell is nothing more or less than a leukocyte, which, 

 in consequence of inflammatory stimuli and positive chemotactic 

 influences, has wandered out of a bloodvessel into the perivascular 

 tissue or into a preexisting or pathologically formed cavity. 1 In 

 inflammatory conditions of the mammary glands an increase in the 

 number of leukocytes in milk must be expected. It appears, on first, 

 thought, that the leukocyte count would aid in the detection of milk 

 derived from a diseased udder, and indicate whether or not it should 



i This subject has been fully discussed in the Chapter on Phagocytosis. 



