no MILK AND ITS HYGIENIC RELATIONS 



quently killing them. Similar methods are employed by the 

 body to defend itself against the presence of red corpuscles belonging 

 to another animal when these are injected. This last method 

 forms a convenient one for investigating many of the problems 

 connected with immunity. The reaction of the body to these 

 different materials is a complex one, more than one substance 

 being involved in the extermination of the invading bacteria or 

 red corpuscles, but to consider this more fully would be beyond 

 the scope of the present work. Each animal organism possesses 

 a certain degree of immunity to the invasion of other substances, 

 differing considerably in different species, and also slightly between 

 different members of the same species. 



The numerous experiments which have been carried out upon 

 milk show that whatever ' protective ' substances may be present 

 in the blood of the mother will pass out in the milk. 



During the colostral period there is a higher content of these 

 substances than in later milk. In view of the connection of these 

 properties with protein, this fact is in accordance with the high 

 protein and antigen content of colostrum compared with that of 

 later milk. 1 



Famulener found that the immune substances in colostrum were 

 actually present in higher amount than in the blood. 



After the colostral period is passed the amount of the protective 

 substances found in the milk is generally greatly reduced. Where, 

 however, the immunity in the mother is of the passive variety, 

 induced by the injection of an antitoxin, the amount present in the 

 milk will depend upon the amount in the blood. 



No precise ratio has been determined between the content of 

 these substances in the blood and in the milk, but it has been 

 found to vary in strength in the milk between ^ to -fa that of the 

 blood. 



There seems no doubt that the absorption of unchanged protein 

 must take place from the alimentary canal of the infant in the 

 early days of life. The properties connected with the production 

 of all forms of immunity are known to be attached to the proteins 

 and to be almost certainly destroyed by digestion. The blood 

 of the young of a mother who has been immunised, does not at 

 birth contain the immune substances possessed by its mother. 

 These, however, are found after suckling has been established, 

 although it has been shown that only a portion of the total amount 

 present in the milk has been absorbed by the young animal as a 

 result of suckling. 



If antitoxin be used, the amount present in the milk can be 

 estimated. The corresponding amount can easily be added to 

 the milk of an unimmunised mother and fed to a control animal, 

 but in this case it is found that the amount absorbed is less than 



Cp. Chap. III. 



