242 MILK 



3. Immunity may be transmitted through the milk from ac- 

 tively immune and passively immunized mothers. 



Antibodies, as a rule, are united with the pseudoglobulin frac- 

 tion of the blood protein. The amount of globulin in normal milk 

 is exceedingly small, and consequently antibodies can exist only 

 in relatively small quantity. The amount of antitoxin found in 

 milk is from one-fifteenth to one-thirtieth the amount contained 

 in the blood. In colostrum the globulin content is much greater 

 than in normal milk, and this fact may account for the relatively 

 large quantity of antibodies in colostrum milk. The globulin 

 content diminishes as lactation progresses and, with this decrease, 

 antibodies also decrease. 



Romer and Much showed that when the mother was injected 

 with tetanus antitoxin during the first seven days after birth the 

 intestinal mucosa of calves allowed ten times as much antitoxin 

 to pass into the circulation as during the fifth to twelfth days. 

 They showed further that when tetanus antitoxin was mixed with 

 milk and fed to calves from bottles the relative amount that 

 passed through the intestinal mucosa was similar to the above 

 results, but the absolute amount was only about one-tenth. This 

 shows that antitoxin mixed with milk does not pass from the 

 digestive tract as readily as when it is injected into the mother and 

 then fed from the breast, or as when the mother has acquired the 

 antitoxic immunity. The authors assume that the horse-serum 

 undergoes a material alteration when passing through the cir- 

 culation of the mother into the milk, and that by this alteration 

 it becomes more readily absorbable by the intestinal mucosa. 



It is clear from these experiments that antitoxin passes into 

 the circulation of the young from the milk whether the mother has 

 been actively or passively immunized. But the amount of anti- 

 toxin that actually passes is substantial only during the first few 

 days after birth. This is due to two causes, namely: 1, To the 

 presence of large quantities of antitoxin-globulin in the early 

 secretion, but the quantity diminishes as lactation progresses; 

 2, to a condition of the intestinal mucosa which permits passage 

 of the globulins and which rapidly disappears. 



The amount of antitoxin in the system of the young is further 

 influenced by the length of the lactation period. In mammals 

 with a lactation period of short duration the amount of antitoxin 

 transmitted through the milk is smaller than in mammals with a 

 long period of lactation. 



It is not definitely known whether antitoxin introduced with 

 milk from a different species of mammal enters the circulation in 

 sufficient quantity to be of real value to the young. There can 

 be little doubt, however, that limited amounts actually pass 



