600 PATHOGENIC MICROORGANISMS 



The problem is plainly of the greatest importance, and for this 

 reason has been diligently investigated during the last few years. The 

 only reliable method of approaching it has been to isolate the tubercle 

 bacilli from diseased human beings and determine for each case whether 

 the organism obtained belonged to the human or bovine type. These 

 types can be differentiated definitely by cultural characteristics and 

 pathogenicity, and it is not likely that the type changes during the 

 sojourn in the human body. Granted this permanence of tyre, it is 

 naturally of much value in revealing the source of an infection, to deter- 

 mine whether or not a human being is harboring a bacillus of the human 

 type or one of the bovine type. 



One of the most valuable contributions made to this problem during 

 the last three years is that of Park and Krumwiede. 33 The above 

 tabulation is taken from their paper and represents a summary of their 

 own cases and those reported by others. 



From this table it is evident that out of a total of 1042 cases, 101 

 only were bovine in origin and over 50 per cent of these occurred in 

 children under five years of age. Fifty-one out of the 59 cases occurring 

 in the 161 infants were directly or indirectly traced to alimentary infec- 

 tion. 



It seems reasonably accurate, therefore, to state the case as follows: 

 Human adults are relatively insusceptible to bovine infection. Such 

 infection can take place, but is unusual. Below sixteen years of age the 

 human race is relatively more susceptible and up to this age the danger 

 of milk infection is unquestionably great, this source accounting for 

 about one-third of the cases. Below five years the danger is greatest. 

 This table alone should form sufficient evidence to silence absolutely 

 any doubts as to the dangers of milk infection and remove any objections 

 to the most rigid sanitary control of milk supplies. 



On the other hand, it also shows that Behring's original claims were 

 far too sweeping and can not be upheld. 



Kober 34 also calls attention to the fact that one must not be deceived 

 into believing that childhood is the only really dangerous age for infec- 

 tion with tuberculosis, and quotes the results of a French committee 

 which, in a small group carefully investigated, found 64 cases in which 

 the disease was transmitted from husband to wife, 43 cases in which it 

 was transmitted from wife to husband, 38 cases transmitted from brother 



R3 Park and Krumwiede, Jour, of Med. Ees., Oct., 1910. 



31 Kober, Repr. No. 309, TJ. S. P. H. S. Reports, October, 1915. 



