No. 6. DEPARTMENT OF AGRICULTURE. 481 



feetion, the figures found in the Registrar-Generars Returns do not 

 support the contention That millc is responsible for all the cases of 

 tabes. It is true that they indicate an increase in the death rate 

 from alimentary tuberculosis among children under twels^e months 

 old, but, on the other hand, there appears to have been a considerable 

 decline in the death rate from the same cause at all ages between 

 one and five years. Now, if tuberculous milk were a frequent cause 

 of tuberculosis, one would not have expected the death rate from 

 that cause to decline among children between one and five years 

 of age, for there is no reason to suppose that there has been any de- 

 cline in the use of cows' milk in the feeding of children at that age 

 during the last fifty years. The fact appears to be that the Reg- 

 istrar-General's Returns do not afford much trustworthy informa- 

 tion with regard to the number of cases of primary alimentary tuber- 

 culosis, and are absolutely worthless as an indication of the extent 

 to which human beings are infected by means of milk. 



There is another direction in which one may turn for evidence on 

 this point. We cannot with any pretence to accuracy ascertain the 

 number of persons that annually become infected by milk, but we 

 may be able to form some estimate of the existing danger in this 

 connection by collecting information as to the frequency with which 

 milk contains tubercle bacilli. We know that about thirty per cent, 

 of all the cows giving milk in this country are tuberculous in some 

 degree. This statement no doubt indicates a deplorable state of 

 affairs, but in the present connection it is not quite so alarming as 

 it at first sight appears. Fortunately not every cow that is tubercu- 

 lous gives milk containing tubercle bacilli. It is true that opinions 

 with regard to this point are not absolutely unanimous, but there is 

 ample evidence to justify the assertion that as a rule the milk is not 

 dangerous until the udder itself becomes diseased. The experiments 

 pointing to an opposite conclusion form only a small minority, and 

 the results obtained in nsost of them were probably due to careless- 

 ness on the part of the experimenter. In a few of the cases in which 

 the milk of an apparently healthy udder was found to be infective, 

 it is probable that the gland tissue was in reality diseased, though 

 not to an extent discoverable without microscopic examination. The 

 important question, therefore, is not what proportion of milch cows 

 are tuberculous, but v»'hat proportion of them have tuberculous 

 udders. Some authorities have estimated this to be as high as ten 

 per cent., but the proportion is certainly much less than that in 

 Great Britain. My own experience leads me to think that about 

 two per cent, of the cows in the milking herds in this country are 

 thus affected. Now, the milk secreted by a tuberculous udder al- 

 ways contains tubercle bacilli, and it sometimes contains enormous 

 numbers of them, and when these facts are apprehended one begins 

 31—6—1901 



