Most of the commissions and official agencies that have considered the precautions to be taken against possible tuberculous meat infection are agreed that the entire carcass of an animal should be condemned when the tuberculous lesions are generalized or when the lesions are extensive in one or both body cavities as well as when the lesions are "multiple, acute, and actively progressive." Any organ showing evidence of tuberculous lesions is obviously not to be passed as food. On the other hand, it is considered that portions of properly inspected animals may be put on the market if the tuberculous lesion is local and limited and the main part of the body is unaffected; in such cases contamination of the meat in dressing must be avoided. It is the general belief that when such precautionary measures are taken the danger of tuberculous infection through properly cooked meat is so slight as to be negligible. Milk is a much more likely vehicle than meat for the transmission of tuberculosis. Freshly drawn raw milk from tuberculous cattle may contain enormous numbers of tubercle bacilli, especially if the udder is diseased. Contamination of milk by the manure of tuberculous cows can also occur. Observers in England, Germany, France, and the United States have found tubercle bacilli in varying numbers in market milk, and have proved that such milk is infectious for laboratory animals. Although, as pointed out with reference to meat infection, the difficulties of tracing any particular case of tuberculosis to its source are very great, there are a number of instances on record in which the circumstantial evidence strongly indicates that milk was the vehicle of infection. Especially convincing are the observations on the relative frequency of infection with bovine and human tubercle bacilli at different ages as shown in the following tabulation:[59] ==================================================================== |Adults Sixteen|Children Five to|Children under | Years Old | Sixteen Years | Five Years | and Over | Old | --------------------+--------------+----------------+-------------- Human tubercle | 677 | 99 | 161 bacilli found | | | Bovine tubercle | 9 | 33 | 59 bacilli found | | | ------------------------------------------------------------------- The large proportion of bovine tubercle bacillus infections in children stands in all probability in causal relation to the relatively extensive use of raw milk in the child's dietary. The proper pasteurization of milk affords a safe and reasonably satisfactory means of preventing tuberculous infection from this source. The general introduction of the pasteurizing process in most American cities has ample justification from the standpoint of the prevention of infection.