Tuberculosis. ' 295 



Tuberculous human beings and animals are sources of further 

 infection only as they throw off materials containing tubercle bacilli. 

 The foci of the disease which exist within the animal,* shut off from 

 the exterior, as tuberculous lymph glands, do not give off bacilli 

 in such a way that they may be transmitted to another animal. 

 For example, the milk of cows which do not have tuberculosis of 

 the udder is harmless even though there are tuberculous lymph 

 glands and serous membranes in the animals ; the meat of a tuber- 

 culous animal is free from danger as long as it does not contain 

 actual tubercles or as long as the lymph nodes situated in the flesh 

 remain free from tubercle bacilli. (For further details consult 

 Ostertag: Zeitsclir. fiir Flcisch- unci Milchhygiene, 1890-1903.) 



Concerning the question of inheritance of tuberculosis, observa- 

 tions running over a number of years upon the condition of calves 

 born of tuberculous cows,' with control by tuberculin injections 

 and slaughtering (Bang), as well as a series of experiments upon 

 pregnant tuberculous guinea pigs (Gartner), give positive informa- 

 tion. Tuberculosis may be acquired through the placenta. Alany 

 examples of this have been found in newly born calves and children, 

 and occasionally too in the miscarried foetus. In such cases the 

 liver and periportal lymph nodes are invariably involved and the 

 disease is apt to be more or less distributed to other lymph glands 

 and organs. When it has been possible to investigate the mother 

 of the tuberculous offspring, invariably a tuberculous affection of 

 the uterus and sometimes of the chorion were found. The tubercle 

 bacillus is scarcely likely to pass directly from the blood of the 

 mother to the foetus (the blood is separate in the two parts of the 

 placenta) ; but if during pregnancy the uterus should become in- 

 volved by tuberculosis (focal, as in one cornu) the tubercle bacilli 

 find their way into the placental milky humor and penetrate the 

 fcEtal placenta, and then pass with the blood of the umbilical vein 

 to the liver of the foetus. In this way the latter is born into the 

 world a subject of tuberculosis; but it is possible that after birth 

 the disease may progress very slowly and remain latent for months. 

 A conceptional or germinal infection, that is through the ovum or 

 spermatozoon, is so improbable that it may be said to be entirely iin- 

 possible. Supposing the possibility that a fertilized ovum could be 

 infected by tubercle bacilli, it would die from the caseating influence 

 of these germs long before it could develop into an embryo, or else 

 the embryo in its earliest stages of germ vesicle and formation 

 of the blastodermic layers would already be but a degenerating mal- 

 formation. When it is remembered that of the millions of sperma- 



